What It Is: 

These Z joints originated from my desire to have a joint that 1) allowed for more rigid constraint of the gantry in the XY plane, but 2) still allowed for some rotational movement in the joints, while 3) reducing the distance in Z from carriage to gantry, and 4) allowing disassembly of joint independent from belt clamping.

Sold as a set of 4.

 Links:

whopping_Voron_mods/z_ball_joints at main · tanaes/whopping_Voron_mods · GitHub