Hi Vlim! Mag tube has no provisions for the spring guide to travel in, and requires a box spring rather then a coil spring? Like an fxo spring? It makes these mags perform pretty well when the correct parts are utilized... Best to you Vlim, til.....lat'r....GT
BTw, it's hard to see until you have it in hand and try to repair... only then is it readily appearant... best, GT