The minimum size the Sentry Strap will fit is roughly 1″ (a buffer tube). The maximum circumference is 8″ (2.6 Max Diameter). The Sentry Strap is secured with Velcro. The sling catch is secured with magnets and will fit anything from padded slings to webbing straps.
Strap Extensions allow the sentry strap to add 1-2 inches to the length of the strap. This allows it to work up to 11 inches