Both of these models are identical in physical appearance except for caliber: Model 20 chambered for 10mm cartridge; Model 21 for .45 ACP. Barrel length on both is 4.60". Model 20 has 15-round clip, weight 26.35 oz.; Model 21 has 13-round clip, weight 25.22 oz. Available with OD green frame. NOTE: Add $25 for Gen4.