Apr. 26, 2021

PSF Stock Index Portfolio

<span style="color:#999999;font-family:Arial;font-size:14pt;margin-left:0%;">SUMMARY: </span><span style="color:#999999;font-family:Arial;font-size:14pt;">PSF STOCK INDEX PORTFOLIO</span><span style="font-family:Arial;font-size:10pt;font-style:italic;margin-left:0%;">Note: Prior to the effective date of this prospectus, the PSF Stock Index Portfolio was named the </span><span style="font-family:Arial;font-size:10pt;font-style:italic;">“Stock Index Portfolio.”</span>

<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;text-transform:uppercase;">INVESTMENT OBJECTIVE</span>

The investment objective of the Portfolio is to achieve investment results that generally correspond to the performance of publicly-traded common stocks.

<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;text-transform:uppercase;">PORTFOLIO FEES AND EXPENSES</span>

The table below shows the fees and expenses that you may pay if you invest in shares of the Portfolio. The table does not include Contract charges. Because Contract charges are not included, the total fees and expenses that you will incur will be higher than the fees and expenses set forth in the table. See your Contract prospectus for more information about Contract charges.

<span style="font-family:Arial;font-size:7.76pt;font-weight:bold;padding-left:0.0%;">Annual Portfolio Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)</span>

<span style="font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;">Example. </span>

The following example is intended to help you compare the cost of investing in the Portfolio with the cost of investing in other mutual funds. The table does not include Contract charges. Because Contract charges are not included, the total fees and expenses that you will incur will be higher than the fees and expenses set forth in the example. See your Contract prospectus for more information about Contract charges.The example assumes that you invest $10,000 in the Portfolio for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the Portfolio’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

<span style="font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;">Portfolio Turnover. </span>

The Portfolio pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs. These costs, which are not reflected in annual portfolio operating expenses or in the example, affect the Portfolio's performance. During the Portfolio's most recent fiscal year ended December 31, the Portfolio's portfolio turnover rate was 4% of the average value of its portfolio.

<span style="color:#000000;font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;text-transform:uppercase;">INVESTMENTS, RISKS AND PERFORMANCE</span><span style="font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;">Principal Investment Strategies. </span>

In pursuing its investment objective, the Portfolio normally invests at least 80% its assets (net assets plus any borrowings made for investment purposes) in common stocks of companies that comprise the S&P 500 Index.The S&P 500 Index represents more than 70% of the total market value of all publicly-traded common stocks. The Portfolio is not “managed” in the traditional sense of using market and economic analyses to select stocks. Rather, the portfolio managers generally purchase stocks in proportion to their weighting in the S&P 500 Index.

<span style="font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;">Principal Risks of Investing in the Portfolio.</span>

The risks summarized below are the principal risks of investing in the Portfolio. All investments have risks to some degree and it is possible that you could lose money by investing in the Portfolio.An investment in the Portfolio is not a deposit with a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. While the Portfolio makes every effort to achieve its objective, the Portfolio cannot guarantee success. The order of the below risk factors does not indicate the significance of any particular risk factor.Derivatives Risk. A derivative is a financial contract, the value of which depends upon, or is derived from, the value of one or more underlying investments, such as an asset, reference rate, or index. The use of derivatives is a highly specialized activity that involves a variety of risks in addition to and greater than those associated with investing directly in securities, including the risk that: the party on the other side of a derivative transaction will be unable to honor its financial obligation; leverage created by investing in derivatives may result in losses to the Portfolio; derivatives may be difficult or impossible for the Portfolio to buy or sell at an opportune time or price, and may be difficult to terminate or otherwise offset; derivatives used for hedging may reduce or magnify losses but also may reduce or eliminate gains; and the price of commodity-linked derivatives may be more volatile than the prices of traditional equity and debt securities.Economic and Market Events Risk. Events in the US and global financial markets, including actions taken by the US Federal Reserve or foreign central banks to stimulate or stabilize economic growth, may at times result in periods of unusually high volatility in a market or a segment of a market, which could negatively impact performance. Reduced liquidity in credit and fixed income markets could adversely affect issuers worldwide.Equity Securities Risk. The value of a particular stock or equity-related security held by the Portfolio could fluctuate, perhaps greatly, in response to a number of factors, such as changes in the issuer’s financial condition or the value of the equity markets or a sector of those markets. Such events may result in losses to the Portfolio.Expense Risk. The actual cost of investing in the Portfolio may be higher than the expenses shown in the “Annual Portfolio Operating Expenses” table above for a variety of reasons, including, for example, if the Portfolio’s average net assets decrease.Index Tracking Risk. The Portfolio’s ability to track the performance and/or holdings and weightings of an index with a high degree of correlation may be affected by, among other things, transaction costs and shareholder purchases and redemptions.Large Company Risk. Large-capitalization stocks as a group could fall out of favor with the market, causing the Portfolio to underperform investments that focus on small- or medium-capitalization stocks. Larger, more established companies may be slow to respond to challenges and may grow more slowly than smaller companies.Liquidity and Valuation Risk. The Portfolio may hold one or more securities for which there are no or few buyers and sellers or the securities are subject to limitations on transfer. The Portfolio may be unable to sell those portfolio holdings at the desired time or price, and may have difficulty determining the value of such securities for the purpose of determining the Portfolio’s net asset value. In such cases, investments owned by the Portfolio may be valued at fair value pursuant to guidelines established by the Trust’s Board of Trustees. No assurance can be given that the fair value prices accurately reflect the value of the security. The Portfolio is subject to a liquidity risk management program, which limits the ability of the Portfolio to invest in illiquid investments.Market and Management Risk. Markets in which the Portfolio invests may experience volatility and go down in value, and possibly sharply and unpredictably. Investment techniques, risk analyses and investment strategies, which may include quantitative models or methods, used by a subadviser in making investment decisions for the Portfolio are subject to human error and may not produce the intended or desired results. The value of the Portfolio’s investments may be negatively affected by the occurrence of domestic or global events,including war, terrorism, environmental disasters, natural disasters or events, political or civil instability, and public health emergencies (such as the spread of infectious diseases, pandemics, or epidemics), among others. Such events may reduce consumer demand or economic output, result in market closures, travel restrictions or quarantines, and significantly adversely impact the economy. There is no guarantee that the investment objective of the Portfolio will be achieved.Regulatory Risk. The Portfolio is subject to a variety of laws and regulations which govern its operations. The Portfolio is subject to regulation by the SEC, and depending on the Portfolio, the CFTC. Similarly, the businesses and other issuers of the securities and other instruments in which the Portfolio invests are also subject to considerable regulation. Changes in laws and regulations may materially impact the Portfolio, a security, business, sector or market.

<span style="font-family:Arial;font-size:10pt;font-weight:bold;margin-left:0%;">Past Performance.</span>

The bar chart and table provide some indication of the risks of investing in the Portfolio by showing changes in the Portfolio's performance from year to year and by showing how the Portfolio's average annual returns for 1, 5, and 10 years compare with those of a broad measure of market performance.Past performance does not mean that the Portfolio will achieve similar results in the future.The annual returns and average annual returns shown in the chart and table are after deduction of expenses and do not include Contract charges. If Contract charges were included, the returns shown would have been lower than those shown. Consult your Contract prospectus for information about Contract charges.Annual return information is provided only for Class I shares. Because all of the Portfolio’s shares are invested in the same portfolio of securities, annual returns for Class III shares would be lower because Class III shares do not have the same expenses as Class I shares.

Annual Total Returns (Class I Shares)

Best Quarter:Worst Quarter:20.51%2nd Quarter 2020-19.67%1st Quarter 2020

<span style="font-family:Arial;font-size:7.76pt;font-weight:bold;">Average Annual Total Returns (For the periods ended December 31, 2020)</span>