Reinsman X-Series Cavalry Shank. Twist SI port with copper rings. 8" cheeks, 5" mouth.
 
"This nice stainless steel cavalry shank is well balanced. the unique ball design will prevent pinching on the corners of the mouth found in most traditional bits. The mouthpiece is designed to get more response out of the horse with less effort from the twist on the bars and the higher port. It provides more leverage, control and stop. The copper adds moisture and softens themouth while the rings pacify a nervous horse. Port height is 2"."