There really aren't too many different sizes available when it comes to how big/small the nozzles tips come with on most tubes of caulk. If you find that the nozzle tip is too big, then just cut it down with a pair of scissors to whatever size suits your needs best. If you are looking for a more permanent method of size modification, then it is possible to buy nozzle tips that offer different sized openings. Those who have the best results using firestop caulk typically use nozzles with opening sizes between .006 – .021 inches wide.