Leupold's Mark 4 Mounting Rings are an excellent mounting option for riflescopes with a 1.0" main tube. These rings are durable, repeatable, and designed to fit most Picatinny or Weaver mounting rail systems. These rings are manufactured from aluminum, and feature torx head cap screws. Torx head screws feature a deep-engaging lobe design that inhibits stripping by ensuring proper driver alignment. These rings are a lighter weight alternative to the standard Mark 4 mounting rings that are made of steel. When you're trying to keep the weight of your gear to a minimum, every ounce counts!