Weaver Picatinny 1/2" Riser Two Piece Set 99658. The Weaver 99658 Picatinny Riser Set combines lightweight construction with sleek ergonomics for a versatile set of mounting options. Constructed using aircraft-grade 6061-T6 Aluminum with Type-III hard anodized coat finish, the Picatinny Riser Set 99658 from Weaver is a durable mount solution. The Weaver 99658 Riser Set features an additional mounting slot which allows you to perfectly position your optic or sight for ideal accuracy and comfort.