Lightly Used Advantage Arms 22LR conversion kit. Fits Glock 17, 17L, 22, 31, 34, 35, 37. This kit WILL work on Gen3 AND Gen4 models as I have the extra guide spring for the GEN4 included. Also included is 3 extra 10rd mags for a total of 4 magazines. I purchased this new and put <300 rounds thru it. Ive used it without any issues on both my Glock 22 (gen3 & gen4).