Aluminium alloy 6061 is a medium to high strength heat-treatable alloy with a strength higher than 6005A. It has very good corrosion resistance  It has medium fatigue strength. 

Applications
Alloy 6061 is typically used for heavy duty structures in:
~ Rail coaches
~ Truck frames
~ Ship building
~ Bridges and Military bridges
~ Aerospace applications including helicopter rotor skins
~ Tube
~ Pylons and Towers
~ Transport
~ Boilermaking
~ Motorboats
~ Rivets

Mount Centerline height 38.1mm

Weight 168grams

This fixed mount with off set of 25.4 mm makes if suitable for giving the correct scope eye relief on rifles like the AR15