... downhole end of a casing string. An integral check valve in the float shoe prevents reverse flow, or U-tubing, of cement ... specifications: 13-3/8" float collar N80, 68 ppf, BTC 9-5/8" float collar N80, 47 ppf, BTC 7" float collar N80, 29 ppf, BTC ... 9 5/8" casing float shoe and float collar