X0306 4 2013-09-09 0 0001443669 Proto Labs Inc PRLB 0001542472 Cleveland Bradley A. 5540 PIONEER CREEK DRIVE MAPLE PLAIN MN 55359 1 1 0 0 President and CEO Common Stock 2013-09-09 4 S 0 12469 73.6034 D 87531 I By JK Cleveland Irrevocable Trust Common Stock 2013-09-09 4 S 0 45623 74.2549 D 41908 I By JK Cleveland Irrevocable Trust Common Stock 2013-09-09 4 S 0 7702 75.0279 D 34206 I By JK Cleveland Irrevocable Trust Common Stock 2013-09-10 4 S 0 20682 74.0734 D 13524 I By JK Cleveland Irrevocable Trust Common Stock 2013-09-10 4 S 0 8524 75.4715 D 5000 I By JK Cleveland Irrevocable Trust Common Stock 95000 I By JK Cleveland Declaration Trust Common Stock 345182 I By Bradley A. Cleveland Declaration Trust Sales effected pursuant to Rule 10b5-1 trading plan adopted by the JK Cleveland IRR Trust ua dtd 12/18/12 (the "Trust") on August 8, 2013. Reflects the weighted average price of 12,469 shares of common stock of Proto Labs, Inc. sold by the Trust in multiple transactions on September 9, 2013 with sale prices ranging from $72.83 to $73.80 per share. The reporting person undertakes to provide upon request byt he U.S. Securities and Exchange Commission staff, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. These shares are held indirectly by a trust for the benefit of the reporting person's children. The reporting person is a trustee of the trust. The reporting person disclaims beneficial ownership of these shares except to the extent of his pecuniary interest in them. Reflects the weighted average price of 45,623 shares of common stock of Proto Labs, Inc. sold by the Trust in multiple transactions on September 9, 2013 with sale prices ranging from $73.84 to $74.84 per share. The reporting person undertakes to provide upon request byt he U.S. Securities and Exchange Commission staff, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. Reflects the weighted average price of 7,702 shares of common stock of Proto Labs, Inc. sold by the Trust in multiple transactions on September 9, 2013 with sale prices ranging from $74.87 to $75.18 per share. The reporting person undertakes to provide upon request byt he U.S. Securities and Exchange Commission staff, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. Reflects the weighted average price of 20,682 shares of common stock of Proto Labs, Inc. sold by the Trust in multiple transactions on September 10, 2013 with sale prices ranging from $73.70 to $74.51 per share. The reporting person undertakes to provide upon request byt he U.S. Securities and Exchange Commission staff, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. Reflects the weighted average price of 8,524 shares of common stock of Proto Labs, Inc. sold by the Trust in multiple transactions on September 10, 2013 with sale prices ranging from $75.00 to $75.98 per share. The reporting person undertakes to provide upon request byt he U.S. Securities and Exchange Commission staff, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. /s/ Mark D. Pihlstrom, Attorney-in-Fact for Bradley A. Cleveland 2013-09-11