I'll take a stab at explaining. Hope I'm right.....Some 1911s with a FLGR that have a very precise/tight fit or an overly lengthened FLGR can be a bit trickier to disassemble the top end. With a standard GR you can push the recoil spring plug inward and turn the barrel bushing and the recoil spring will force the recoil spring plug out and then you can remove the spring itself. The standard length GR should then fall out. A FLGR has to slide out due to its length. Also, if the FLGR is a bit too long then you won't be able to push the recoil spring plug inward far enough to be able to turn and remove the barrel bushing. Some FLGR have a hole drilled in them so you can insert a paperclip bent at a 90 degree angle into the hole with the FLGR and recoil spring pushed forward toward the muzzle end. It locks the recoil spring on to the FLGR and then you can remove the entire FLGR and spring and recoil spring plug in one piece out the rear of the slide. It's more complicated or time consuming then a standard GR disassembly. Again not all FLGR's have to be removed like this. Hope I'm accurate with my description and that it helps!