The Manson Precision 12 Gauge Thinwall Reamer is designed for easy choke tube installation on a lathe for superior results, although it can be used by hand.
This tooling includes precision ground tap and reamer from high-speed steel with interchangeable pilot bushings for accurate bore alignment.
It is specifically made for 12 gauge shotguns and is compatible with thinwall-style tubes only, being about .020" thinner than standard Tru-Choke tubes.