APA's patented Tru-Loc scope rings are built to higher standards than any other scope rings on the market to date. Each individual ring matches perfectly to any other ring of its size meaning no "matched sets". Unlike most scope rings the Tru-Loc scope rings have the ability to return to zero after being removed from a rifle. Also, no more guessing games when it comes to what size you need with precisely measured height choices not vague small, medium or large. MADE FROM 7075 ALUMINUM AND AVAILABLE IN 30MM AND 34MM IN A RANGE OF HEIGHTS.