What size bridle for my horse?? Please help!?

I have a 17.5 hand Thoroughbred stallion. I am looking to by him a new bridle and am wondering what size of bridle to get. His halter size is over sized so what size do i get him? I have seen sizes like Warmblood, Cob, Horse, and Oversize. I am looking at a Harmohn bridle is this a good quality bridle? If not what is a good quality bridle for pleasure and jumping. Thank you so much and God Bless.