Just got them yesterday. This is substantial hardware, well engineered and made. A dedicated closed center channel for the strap keeps the claw from ever slipping off, the underside of the claw is grooved with angled edges to dig into rubber tread and even has an arc to conform to the tire curvature. The material is thick! The claw looks to be 6XXX series aluminum (with small percentages of magnesium and silicon as markers), i.e., what is considered to be ‘aircraft grade’, and hardness indicates optimum temper, with ~45 ksi tensile strength.
No buyer’s regrets here, the things are nasty! Wouldn’t be easy to come up with a home brew design to match these.
One modification I’ll make will be to drill and tap for a set screw in each one to keep the extenders from possibly slipping out and taking off during wheel spin; don’t want to leave anything to chance with regard to flying projectile scenarios, or lose them in muck or snow.