The Pelham was designed to be used with two reins, one attached to the top ring (snaffle) and the other attached to the bottom ring (curb), which is used when extra leverage is needed. It can also be used with rounding attached to a single rein, so that the snaffle and curb come into action at the same time. The medium mouthpiece arches over the center of the mouth, creating more space, which is ideal for horses with a wider tongue. The small ring above the bridle is used for a lip strap which is not essential but is correct for showing and helps keep the curb chain flat. The Pelham is ideal for stronger horses who can benefit from the activation of the bridle rein which puts pressure on the mouth bars, chin, muzzle and arch of the mouth to promote correct head carriage. MeasurementsAccording to our size guide, the A and B measurements of this bit are as follows:4.5" - A=14mm & B=115mm5" & 5.5" - A=14mm & B=130mm6" - A=14mm & B=140mm Stainless Steel Horse Bits...Stainle...