Troy does not provide that specification on their website or to us. You would need to contact the manufacturer directly for that information.
1-9/16" inside diameter
I just got mine today and was worried about the inside diameter and being able to fit over the Strike Industries oppressor. It fits with not much wiggle room.
Inside diameter is 1.39" and Outside Diameter is 1.75". Also, it weighs 10.20 oz according to Troy.