If they are authentic tripod 700s, or a faithful reproduction, they take what's known as a P45 or type A base; that's not the same as an H4 base. You used to be able to buy a halogen capsule on a P45 base with ease, but I suspect that no one has bothered to make a P45 base for LED emitters... But check your housings before taking my word for it! Best, chris