Burris 420223 XTR Sig Rings, 30mm, 1.5" Height, Pair, Matte Black Unique, self-centering, dual steel clamps with full cross-through connection assure proper center on any width Pica tinny rail, while adding extra strength Revolutionary pops-align inserts technology, in a tactical ring configuration Pops-align inserts guarantee perfect centering and maximum scope-to-ring contact for tremendous gripping power without damaging the scope finish