The art of fitting a double bridle bit correctly.

The most important bit size is the Weymouth which must allow the horse to move inside the cheeks freely if the cheeks are too tight on the face your horse cant flex and will be reluctant to bend especially going sideways as the top of the Weymouth cheek will dig into the horses cheek just above the corner of the lips and inhibit flexion.

You should be able to stand in front of your horse and run your thumbs on both sides of the face at the same time between your horses face and the top of the Weymouth cheek.

And then the Bradoon can be the same size as the Weymouth on a fine faced Horse and 1/4" bigger on larger fleshier and wider jawed horse.

So if your horse normally wears a 5.25 bit then the Weymouth should be this size and then choose a 5.25 Bradoon or a 5.5 Bradoon.

If you feel a 5.25 Weymouth might be a little snug above the corner of the lip then choose a 5.5 Weymouth and a 5.5 or a 5.75 Bradoon