the triangular left-side folding stock first appeared on the russian model aks-74, as a paratrooper/mechanized infantry option. it was utilized, later, on the aks-74u krinkov.

it was copied by the bulgarians. the bulgarians still manufacture the stock for use on krinkovs.

production life in russia was short lived on the aks-74, as it was replaced by the left-side folding polymer buttstock. the triangular metal folder is also seen on other weapons, such as the bizon.