In addition to MiPS and WaveCell, 6D has a proprietary slip plane design between two crush layers. Leatt and Kali also have helmets with liner "doughnuts" designed to permit head motion on impact. POC has their SPIN system, LEM uses something called "GelMotion" impact pads. Laser has a design called KinetiCore. Custom helmet producer HEXR has 3D printed honeycomb interior that reduces rotational energy. Louis Garneau has a design called ROTEXX with a fluid layer. There are others, like Smith Optics' Koroyd liner.

BTW, I've seen posters (not Jay) insinuate that MIPS itself was a safety certification or its presence was some sort of guarantor, when in fact it's just a proprietary, licensable slip plane design. The Triple 8 Dual Certified MIPS helmet is rated just three stars in the Virginia Tech tests, currently the #185th place tested helmet!

Some smart, sincere folks at ASTM, Snell, CPSC, Consumer Reports and Virginia Tech have designed tests they say mimic cycle crashes. All five test protocols differ in various aspects. There are disputes over whether the EN960 headform or the Hybrid III headform more accurately mimics the human head in testing.