The bases are "BB's" early steel not the later "BA's" front aluminum rear alloy steel. You need RBHS.3 for 1" scopes or RBHS.4 for 26mm scope. lower rings in most cases won't give the scope clearance. A much rarer setup and generally found on the early Parker Hale Supreme sporters. Was a good solid a set up despite's its appearance. Relied on the stiffness of the steel bodied scopes. Ron (Canada)