Mouth piece 62% copper to promote chewing and flow of saliva. The copper alloy is nickel-free, Rings stainless steel. Thickness 1.8cm Ring Width: 7cm. Stainless steel rings. The new bit from Waldhausen contains 62% copper which stimulates the horse's salivation and chewing. The alloy is nickel-free, and the rings are made of stainless steel. Thickness: 18 mm. The thickness is 16 mm for size 11.