Designed and developed by ZRTS, these basepads add 10rds to your magazine capacity giving you a maximum of 40+1 in the 9mm SIG MPX. Our basepads add 10 rounds to any length mag. Turns a 20rd into a 30! 10 into a 20, 30 into a 40! The basepads are easily removed in the field without tools for cleaning, breakdown, etc. ZRTS Basepads are the ONLY ones on the market with an internal spring guide to protect against pinch and premature failure of the magazine spring! Bottom is machined out for our grit tape numbers. Black color is anodized.