The MB 32-3 is an alternative to the traditional mullen. It has three barrels, which turn the mouthpiece from the typical solid bar of a mullen into a flexible bar, which allows the horse to elevate his tongue and swallow more easily. When the reins are engaged, the mouthpiece becomes a solid bar like a traditional mullen but with an exaggerated curve. This curved bar rotates across the bars and lips down onto the tongue, applying pressure across the entire surface of the tongue.
This bit has the D side which has hooks.
Myler bits come in 1/2 inch measurements, but this bit comes up slightly larger at 5.75. Actual measurement shown in the pictures.