X0508 4 2023-09-07 0001781162 Momentus Inc. MNTS 0001751631 Prime Movers Lab Fund I LP P.O. BOX 12829 JACKSON WY 83002 0 0 1 0 0001875411 Sloss Dakin C/O PRIME MOVERS LAB, P.O. BOX 12829 JACKSON WY 83002 0 0 1 0 0001838981 Prime Movers Growth Fund I LP P.O. BOX 12829 JACKSON WY 83002 0 0 1 0 0001780632 Momentus PML SPV 1 LP C/O PRIME MOVERS LAB, P.O. BOX 12829 JACKSON WY 83002 0 0 1 0 0001819327 MOMENTUS PML SPV 2 LP C/O PRIME MOVERS LAB, P.O. BOX 12829 JACKSON WY 83002 0 0 1 0 0001853076 Momentus PML SPV 3 LP C/O PRIME MOVERS LAB, P.O. BOX 12829 JACKSON WY 83002 0 0 1 0 0 Class A common stock 2023-09-07 4 S 0 11748 6.5075 D 234295 D Class A common stock 2023-09-07 4 S 0 4656 6.5075 D 92871 I Held by Momentus PML SPV 1 LP Class A common stock 2023-09-07 4 S 0 917 6.5075 D 18300 I Held by Momentus PML SPV 2 LP Class A common stock 2023-09-07 4 S 0 2276 6.5075 D 45387 I Held by Momentus PML SPV 3 LP Class A common stock 2023-09-07 4 S 0 906 6.5075 D 18080 I Held by Prime Movers Growth Fund I LP Class A common stock 2023-09-08 4 S 0 6269 5.8145 D 228026 D Class A common stock 2023-09-08 4 S 0 2485 5.8145 D 90386 I Held by Momentus PML SPV 1 LP Class A Common Stock 2023-09-08 4 S 0 490 5.8145 D 17810 I Held by Momentus PML SPV 2 LP Class A Common Stock 2023-09-08 4 S 0 1215 5.8145 D 44172 I Held by Momentus PML SPV 3 LP Class A Common Stock 2023-09-08 4 S 0 484 5.8145 D 17596 I Held by Prime Movers Growth Fund I LP Class A Common Stock 2023-09-11 4 S 0 4526 5.5697 D 223500 D Class A Common Stock 2023-09-11 4 S 0 1794 5.5697 D 88592 I Held by Momentus PML SPV 1 LP Class A Common Stock 2023-09-11 4 S 0 354 5.5697 D 17456 I Held by Momentus PML SPV 2 LP Class A Common Stock 2023-09-11 4 S 0 877 5.5697 D 43295 I Held by Momentus PML SPV 3 LP Class A Common Stock 2023-09-11 4 S 0 349 5.5697 D 17247 I Held by Prime Movers Growth Fund I LP Held by Prime Movers Lab Fund I LP ("PML"). Prime Movers Lab GP I LLC ("PML GP") is the general partner of PML. Held by Momentus PML SPV 1 LP ("PML SPV 1"). PML GP is the general partner of PML SPV 1. Held by Momentus PML SPV 2 LP ("PML SPV 2"). Prime Movers Lab GP II LLC ("PML GP II") is the general partner of PML SPV 2. Held by Momentus PML SPV 3 LP ("PML SPV 3"). PML GP II is the general partner of PML SPV 3. Held by Prime Movers Growth Fund I LP ("PM Growth"). Prime Movers Growth GP I LLC ("PM Growth GP") is the general partner of PM Growth. Dakin Sloss is the manager of PML GP, PML GP II and PM Growth GP, and may be deemed to beneficially own the securities held by PML, PML SPV 1, PML SPV 2, PML SPV 3 and PM Growth. Mr. Sloss disclaims any beneficial ownership of the securities reported herein for purposes of Section 16 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of its pecuniary interest therein. The price of $6.5075 per share represents a weighted average of purchase prices ranging from $6.010 to $7.350 per share. The reporting person undertakes to provide upon request by the Commission staff, the issuer, or a security holder of the issuer, full information regarding the number of shares purchased or sold at each separate price. The price of $5.8145 per share represents a weighted average of purchase prices ranging from $5.445 to $6.558 per share. The reporting person undertakes to provide upon request by the Commission staff, the issuer, or a security holder of the issuer, full information regarding the number of shares purchased or sold at each separate price. The price of $5.5697 per share represents a weighted average of purchase prices ranging from $5.271 to $5.81 per share. The reporting person undertakes to provide upon request by the Commission staff, the issuer, or a security holder of the issuer, full information regarding the number of shares purchased or sold at each separate price. /s/ Taylor Frankel, Authorized Person on behalf of the General Partner of each Reporting Person 2023-09-11 Dakin Sloss /s/ Taylor Frankel, Attorney-in-fact 2023-09-11