Thanks for the reply - I tried searching your posts to find it but it was after midnight gave up and searched brownells and found it. I think the difference is the way they mount to the rifle

"Easy, no gunsmithing installation, replaces the sight rib on Models 1A, 1S and 1H. Front base is machined to accept the factory rear sight leaf. Models for 1V and 1B replace factory bases." from brownells site.

Gonna call them now and find out. Thanks alot will post the contact info and pertinent info so others can find it

mike