Driving Bits:

Liverpools are the most widely used of all driving bits. The swivel cheeks, tends to keep the mouth more responsive. Liverpool bits offer different rein slots for maximum adjust ability. 

Fixed Cheeks do not allow the cheeks to swivel and are typically used with a pair of horses. This avoids the pinching of the lips that can occur with the coupling reins. 

Military/Elbow bits have cheeks that are set back at a square angel so that a horse can't grab the shank with his teeth or lips. This design helps prevent pinching of the lips which makes it a good choice for pair driving.

Butterfly are available in 2 or 3 loop styles. They offer several rein placement options and give the horse an opportunity to respond to a lighter cue initially. 

Cherry Roller & Copper Barrels have a series of copper rollers that encourage the horse not to mouth the bit. Rollers make it more difficult for the horse to take hold of the bit - rollers just slip away.