The JE Machine Tech AR-15/AR10 Mil-Spec 6-Position Buffer Tube is a standard Milspec 7.25" tube.
It is carbine length and yes this is compatible with an AR-15.
Please reach out to the manufacturer as this information is not made available. (909) 972-6545
The inner diameter is the standard 1" milspec diameter.
It is a mil-spec buffer tube.
This is made in the USA.