Designed to fit MILSPEC Buffer tubes. The BKF SOPMOD Features an excellent cheek weld for optimum shooting positioning. Within the stock frame are two water-tight storage compartments for small items(batteries). The rubber-padded buttplate provides a non-slip surface for consistent shoulder and cheek placement. BKF has taken features the user’s demand and offered them a light, compact buttstock at a very attractive price point. Perfect for your MK18 clone builds!