dubojr1, when I ordered the Thermo-Bob kit ordered the 3/4" hose Thermo-Bob unit and 3/4" hose By-Pass tee. Cut the small by-pass hose to 10 1/4" long. You will find the original upper radiator hose to be 3/4" ID and the lower radiator hose to be 7/8" ID. Have not had any problems using the 3/4" tee with the original 7/8"ID radiator hose.