Underfolder AK-47s are AK-47 variants with a stock that folds beneath the receiver, shortening the rifle for storage and transport. They're chambered in 7.62x39mm and keep the standard AK layout. The folding stock collapses under the receiver and extends to a fixed shooting position. The receiver is stamped steel. Most underfolder AKs use the usual AK parts: a chrome-lined barrel, adjustable iron sights, and standard AK magazines and accessories. The trade-off is the stock itself. Underfolder stocks are thinner and less comfortable than a fixed or side-folding stock, but they pack down smaller. They're common among collectors and shooters who want a more compact AK for storage or range use.