Many ball gags on the market today have large, solid rubber balls which make the gag uncomfortable to use for any length of time.
The ball on this gag has a soft rubber shell with a compressible foam inner which makes it much more comfortable than most as it fills the mouth but does not force the jaws wide open.
It also has a soft leather strap securing the gag ball in the mouth.
The black ball is about 1 1/4 inches (3.2 cm) in diameter, the red ball is slightly larger at 1 1/2 inches (3.8 cm)