They are unique SKS rifles that accept AK mags with a bit f modification. The long monte carlo stock fits some folks very well and is too long for others.
They can be pricey and if $500 or more it might be better to add a couple more hundred and get a nice AK. I had one for several years and sold it last year. Did not shoot it that much over other SKS's I own or the AKM's etc.
Why? Are you collecting SKSs'? There's nothing wrong with having a Chicom SKS but if your buying one because of the mag then its pointless imo. There is already a solution to the SKS with a detachable mag.....its the AK. If you still want a short stroke piston....VZ!