Foley catheters are human urinary balloon catheters. They are 45 cm long and the diameter varies from 12 French gauge (1 French gauge = 0.3 mm) to 24 French gauge. A 20 French gauge is most commonly used in cows, while in heifer a 16 French gauge catheter is is used. The balloon is distended with air or with flushing medium; approximately 15 cc in cows, approximately 12 cc in heifers.
Drost M (1976)