A boot for protecting the male and female elements of a transmission joint, one element is formed by a transmission shaft having radial arms for carrying rollers, the other is formed by a bell housing suitable for at least partially receiving the rollers suitable to be inserted into the bell housing's open end, the boot, has an elongate hollow body enabling the shaft to pass there through, with a “first” one of its ends suitable for being secured to the shaft, and its “second” end suitable for being positioned in overlapping and interfitting manner over the bell housing's open end. This boot has an internal peripheral shoulder, whose surface that faces towards the second end of the boot is provided with at least two recesses which open towards the second end, the inside of each recess forming a seat having a concave bearing surface for receiving a roller in thrusting contact.