Snaffle bits

The way a bit fits in your horses mouth can effect even the best trained horse.
A bit should have a 1/8 (3 mm) to a 1/4 (6 mm) inch gap on both sides of the horses mouth, allowing for controlled movement and to avoiding pinching.
The standard mouthpiece widths are 5'' (12,7 cm) and 5 1/8" (13 cm).