The Shield Arms Glock 43X / 48 +5 Magazine Extension is a precision-machined 6061 aluminum magazine extension that adds 5 rounds of capacity to the new Glock 43X and Glock 48 OEM 15-round magazine - bringing total capacity to 20 rounds. IMPORTANT NOTE: It is compatible with the OEM 15-round magazine only and is not compatible with OEM 10-round magazines or Shield Arms S-Series magazines. Compatible with: Glock 43X and Glock 48 OEM 15-round magazines only Not compatible with: OEM 10-round magazines or Shield Arms S-Series magazines Includes a plus-power replacement spring and all installation hardware Backed by Shield Arms' lifetime warranty and Spring for Life guarantee Magazine NOT included