You use a Weymouth bradoon in combination with a Weymouth curb bit for a Weymouth bridle. A bradoon is usually thinner and has smaller rings than a normal bit. The horse only has a limited space in the mouth, so a thinner snaffle is more comfortable for your horse. The size of the Weymouth bradoon depends on the horse's mouth and does not always have to be larger than the curb bit.
There are various variants available in different materials. If you normally ride with a single broken bit, you usually also use a single broken bradoon because your horse is used to that. Usually the choice is made for the same material for both bits. BR has an extensive choice of stainless steel, Cuprigan and Cuprion for both the bradoon and the curb bit.