I don't know why I am bothering to answer this because it is so old, but oh well.
for regular snaffle bridles you can use:
1.ordinary snaffle with single-jointed mouthpiece
2.ordinary snaffle with double-jointed mouthpiece
3.racing snaffle (D-ring)
4.snaffle A)with cheeks, with or without keepers
B)without cheeks (egg-butt)
5.snaffle with upper or lower cheeks
6.unjointed snaffle (mullen mouth)
7.snaffle with cheeks. (hanging or drop cheek; Baucher). This may be a D-ring or other ordinary snaffle
10. French snaffle
11. Snaffle with rotating mouthpiece
they may be made with a rubber, plastic or leather covering, but the bit may not be modified by adding latex of other material. bits with mouthpieces made of synthetic material are permitted, provided that the contours of the bit conform to the contours of one of bits mentioned above. flexible rubber or synthetic mouthpieces are permitted.
no twists, no wire, no Pelham, no gag, and unfortunatley most myler bits are illegal.