The ideal companion for the 57SML receiver sight the 17 comes complete with a set of 8 interchangeable inserts. The 17AML fits low to the barrel with a height of .494". The 17ATC fits rifles that use a tall vernier type rear sight. The 17ATC has a height of .852". All 17's are machined from steel and have a standard 3/8 dovetail.
(Except 17AEU which has European Dovetail for Lyman Muzzleloaders).