This is a NCSTAR Bag known as the Shotgun Scabbard, model CVSCB2917T.
The Tactical Shotgun Scabbard is designed for an easy" comfortable" and secure way of carrying a shotgun over the shoulder or for modular mounting onto MOLLE compatible gear.
Features:
MOLLE Webbing on Both Sides
Adjustable Retention Strap
Padded Shoulder Sling