All thee of the Compact M2.0s I've had; 9mm 3.6", 9mm 4", 9mm 4" OR, had springs on the slide stop and none of the six full size M2.0s; 9mm 4.25", 9mm threaded, 9mm 5", .40 4.25", 9mm 4.25" OR, 9mm 5" OR, have had the spring. Two of the three OR had the extended/wider slide stop, one compact and one full size.