Pearce Grip Grip Extension, Fits Glock Gen 4, 9/40/357 Sig, 45 GAP, Black PGG4PLUS This unit adds capacity to Generation 4 & 5 Sub-Compact" Mid" and Full Size Glock high capacity magazines. This magazine extension replaces the original floor plate and internal locking plate and adds two rounds to a 9mm; two rounds to a 40SW and 357SIG" and one round to a 45GAP magazine. This unit will not fit the 10mm or 45ACP models.