Specs:

T2 male thread (M42x0.75) on one side, to attach the adapter to T-2 accessories.
The other end is a 2" nosepiece with both internal T-2 threads, which enable even more uses in a T-2 arrangement,  and 48mm filter threads (M48x0.75)

The latest version now incorporates a removable 'stop ring', which means the nosepiece can now be used fully inside your 2" barrels and will minimise optical length.