<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-11-30</periodOfReport>

    <issuer>
        <issuerCik>0001324948</issuerCik>
        <issuerName>RBC Bearings INC</issuerName>
        <issuerTradingSymbol>ROLL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001256535</rptOwnerCik>
            <rptOwnerName>HARTNETT MICHAEL J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>102 WILLENBROCK ROAD</rptOwnerStreet1>
            <rptOwnerStreet2>ONE TRIBOLOGY CENTER</rptOwnerStreet2>
            <rptOwnerCity>OXFORD</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06478</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>true</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
            <officerTitle>President and CEO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2020-11-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>38744</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>168.8299</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>358741</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2020-12-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>21337</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>168.2411</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>337404</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>72.83</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2020-07-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2022-07-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>16000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>16000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>72.94</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2020-07-08</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2023-07-08</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>40000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>40000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>99.64</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2020-06-27</value>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2024-06-27</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>48000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>48000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>132.12</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2019-06-07</value>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <value>2025-06-07</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>76000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>76000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>143.92</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2020-06-03</value>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <value>2026-06-03</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>76000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>76000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Option to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>137.44</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2021-06-02</value>
                <footnoteId id="F7"/>
            </exerciseDate>
            <expirationDate>
                <value>2027-06-02</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>58892</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>58892</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Sold pursuant to a 10b5-1 plan.</footnote>
        <footnote id="F2">Includes 79,143 shares of restricted stock, which vest according to the following schedule; 17,347 shares vest on 6/7/2021; 34,693 shares 1/2 of which vest on 6/3/2021 and 1/2 vest on 6/3/2022; and 27,103 shares 1/3 of which vest on 6/2/2021, 1/3 vest on 6/2/2022 and 1/3 vest on 6/2/2023.</footnote>
        <footnote id="F3">All these options to purchase Common Stock are exercisable except for 20,000 options that vest on 7/8/2021.</footnote>
        <footnote id="F4">All these options to purchase Common Stock are exercisable except for 32,000 options that are subject to the following vesting schedule - 1/2 vest on 6/27/2021 and 1/2 vest on 6/27/2022.</footnote>
        <footnote id="F5">All these options to purchase Common Stock are exercisable except for 45,600 options that are subject to the following vesting schedule - 1/3 vest on 6/7/2021, 1/3 vest on 6/7/2022 and 1/3 vest on 6/7/2023.</footnote>
        <footnote id="F6">All these options to purchase Common Stock are exerciseable except for 60,800 options that are subject to the following vesting schedule - 1/4 vest on 6/3/2021, 1/4 vest on 6/3/2022, 1/4 vest on 6/3/2023 and 1/4 vest on 6/3/2024.</footnote>
        <footnote id="F7">These options to purchase Common Stock are subject to the following vesting schedule - 1/5 vest on 6/2/2021, 1/5 vest on 6/2/2022, 1/5 vest on 6/2/2023, 1/5 vest on 6/2/2024 and 1/5 vest on 6/2/2025.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/John J. Feeney/attorney in fact</signatureName>
        <signatureDate>2020-12-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
