The PTS Enhanced Polymer Stock (EPS) is a full-function collapsible polymer stock that offers lots of flexibility. The side storage compartment measures 139 mm x 31 mm, enough space to fit a butterfly style or mini type battery. There are multiple sling mounting options featured on the stock including QD swivel sockets on both sides with a pass-through channel for loop-type sling attachments and a sling slot on the front side of the butt part of the stock. The EPS Stock is compatible with almost all AEG and GBBR buffer tubes.