Woof Wear's 3-digit Bridle Number Holder is a great way of displaying numbers when competing. It is secured using hook & Loop straps that wrap around the bridle. The numbers are printed on tough waterproof fabric which is cleverly folded so changing numbers is effortless.
My mare is very fussy about her fly masks and I have tried many brands before finally finding the Woof wear one. She is finally comfortable with it on and doesn't scratch it off on the nearest tree. It keeps it's shape nicely and matches her black colour.