The SIG SAUER SIG556 HOLO featured a holographic sighting system that allows for quick target acquisition, with four illuminated reticle patterns with adjustable intensities. It has a proven two-position adjustable gas valve system joined to a lightweight alloy trigger housing that accepts standard AR magazines. The vented non-slip polymer forearm has three picatinny rails for accessory mounting. The SIG556 stock is collapsible and has a rubber butt pad and a number of sling attachement points.