Large Couplers
Now discontinued, the Large Couplers were made from 2" x 1" x 3/4" solid blocks of 7075 aircraft alloy aluminum. 7075 is the premium grade of aircraft alloy aluminum, endowed with extreme hardness and strength (actually greater than some steels), and was chosen as well for its excellent thermal transmission and self-damping characteristics (7075 is the same material used in the Rollerblock Series 2+ and also Rollerblock Jr. HDSE bodies, and for the same reasons). Each Large Coupler was cut from a solid bar of 7075 aluminum, then hand finished. There were two standard varieties: Large Couplers, and Supercouplers.
Most Symposium Platforms were supplied with Large Couplers; qualified Ultra and Super Plus platforms are now supplied with improved Precision Couplers.