The Buster Roller is a great bit for schooling, the link in the middle is shortened to 40mm increasing bar and tongue pressure making the bit sharper than conventional link bits.
The increased pressure on the bar will lift the head and the roller will increase pressure on the tongue tucking the chin in.
Best suited for a horse with a low head carriage and which leans on the bit.
The Pelham has attachments for two reins, one near the mouthpiece and one at the end of the shank. These reins have similar action to the curb and bradoon reins in the double bridle.