DR024 Diamond R by Reinsman Tom Thumb Copper Mouth BitDiamond R by Reinsman Tom Thumb Copper Mouth Bit Tom Thumb bit 5 Mouth 6. 5 Cheeks Copper mouth to increase salivation which creates a more responsive mouth. This bit can be severe so ride with gentle hands. A curb strap is recommended for training and western style riding. Diamond R products are designed and manufactured to Reinsmans specifications and quality standards. Products were developed to provide a value priced option to all riders.