rad hoses 2" and 2.5" from a Semi Truck repair shop. i guess they use those sizes in their trucks. the inside of the hose is perfect silicone and the outside is black woven material. they are not great, and i do have some blue ones on the way, but they do the trick for now, and work perfectly!!! just FYI for those of you DIY's who are cheap like me. cost me 6.00 total