Formally called the Super X Dance plug – smaller 5/16″
Newer Power Plug larger 5/8″ and this is the more common size.

5/16″ fits Sure Grip plates Super X, Jogger, and Probe 5/16 style

5/8″ fits Sure Grip plates Probe 5/8, Rock, Avenger, Avanti, Competitor, Century, Classic, Cyclone, XK4, Laser, Power Trac, and Snyder,

Smaller version will fit the Super X plate where the larger 5/8″ plug will fit plates that use the standard adjustable toe stops.

All made in the USA.