Tack

Before choosing a bit you will want to learn the parts of a bit and materials bits are made from and what actions they apply....

Sweet iron mouthpieces are made to rust.

You can use a bit-measuring tool, or, if you don’t have access to this tool, you can take a piece of string and mark the points on the string at the edge of your horse's mouth. Once you have this marked, measure the marks on a ruler, and you will have a general idea of what size bit your horse will need.