These machined aluminum nipples are great for splicing our silicone coolant hose. They are useful when connecting an elbow to a straight section, connecting two elbows, or connecting a reducer to an elbow. The ridges are aggressive enough to insure good retention when used with our Lined Hose Clamps (Part No. 3613-1.75, sold separately) but not so aggressive as to cause cuts in the hose. Ridge configuration may vary from photo.