X0306 4 2012-08-22 0 0001443669 Proto Labs Inc PRLB 0001542779 NBGE Manager, LLC C/O NORTH BRIDGE GROWTH EQUITY 950 WINTER STREET, SUITE 4600 WALTHAM MA 02454 0 0 1 0 0001542781 NBGE GP, LLC C/O NORTH BRIDGE GROWTH EQUITY 950 WINTER STREET, SUITE 4600 WALTHAM MA 02454 0 0 1 0 0001390657 NORTH BRIDGE GROWTH EQUITY I LP C/O NORTH BRIDGE GROWTH EQUITY 950 WINTER STREET, SUITE 4600 WALTHAM MA 02454 0 0 1 0 0001542785 North Bridge Growth Management, L.P. C/O NORTH BRIDGE GROWTH EQUITY 950 WINTER STREET, SUITE 4600 WALTHAM MA 02454 0 0 1 0 0001218581 ANDERSON EDWARD T C/O NORTH BRIDGE GROWTH EQUITY 950 WINTER STREET, SUITE 4600 WALTHAM MA 02454 0 0 1 0 0001206641 DAMORE RICHARD A C/O NORTH BRIDGE GROWTH EQUITY 950 WINTER STREET, SUITE 4600 WALTHAM MA 02454 0 0 1 0 Common Stock 2012-08-22 4 J 0 1600000 0.00 D 4821790 I By North Bridge Growth Equity I, L.P. Common Stock 1126 D Common Stock 610 D Common Stock 585 I By Angel 2011 Dynasty Trust The transaction reported on this Form 4 represents a pro rata distribution, and not a purchase or sale of securities, by North Bridge Growth Equity I, L.P. to its general and limited partners without consideration. Represents shares held directly by North Bridge Growth Equity I, L.P. NBGE Manager, LLC ("NBGE") is the managing manager of NBGE GP, LLC, which is the sole general partner of North Bridge Growth Management, L.P., which is the sole general partner of North Bridge Growth Equity I, L.P. NBGE has sole vesting and dispositive power over such shares. Shared voting and investment power over such shares is vested in the managers of NBGE, Edward Anderson and Richard D'Amore. Mr. Anderson and Mr. D'Amore each disclaim any beneficial ownership of such shares, except to the extent of any pecuniary interest therein. This report shall not be deemed an admission that any of the reporting persons is the beneficial owner of such securities for purposes of Section 16 or for any other purpose. Represents shares held of record by Mr. Anderson received in connection with the pro rata distribution from North Bridge Growth Equity I, L.P. referenced in footnote 1 above. Represents shares held of record by Mr. D'Amore received in connection with the pro rata distribution from North Bridge Growth Equity I, L.P. referenced in footnote 1 above. Represents shares held of record by a trust for the benefit of certain of Mr. Anderson's immediate family members which were received in connection with the pro rata distribution from North Bridge Growth Equity I, L.P. referenced in footnote 1 above. Mr. Anderson's immediate family member is the trustee of the trust. Mr. Anderson disclaims beneficial ownership of these shares, and the filing of this report is not an admission that Mr. Anderson is the beneficial owner of these securities for purposes of Section 16 or any other purpose. /s/ Julie M. Regnier, Attorney-in-Fact for NBGE Manager, LLC 2012-08-24 Julie M. Regnier, Attorney-in-Fact for NBGE GP, LLC 2012-08-24 Julie M. Regnier, Attorney-in-Fact for North Bridge Growth Equity I, L.P. 2012-08-24 Julie M. Regnier, Attorney-in-Fact for North Bridge Growth Management, L.P. 2012-08-24 Julie M. Regnier, Attorney-in-Fact for Edward Anderson 2012-08-24 Julie M. Regnier, Attorney-in-Fact for Richard D'Amore 2012-08-24