Pearce Grip Grip Extension, Fits Glock Mid/Full Size +3 9mm,+2 40sw,+1 45gap, Black PGGP-MID This unit adds capacity to Mid and Full Size Glock high capacity magazines. This magazine extension replaces the original floor plate and internal locking plate and adds three rounds to a 9mm; two rounds to a 40SW and 357SIG" and one round to a 45GAP magazine.