Designed for in-place resistance swim training while using lane lines, to train for proper hip rotation; critical to stroke efficiency. Several can be used in one lane at time. Coaches can assist with positioning and stroke while swimmer is stationary. Use in home swimming spas where jets are not too powerful. A comfortable waist belt that fits up to 44-in (1.1 m) waist with two, 2-ft (60 cm) tubes and 2.5-ft (76 cm) of adjustablewebbing with clips on each side. Available in green resistance level (8 - 24 lbs / 3.6 - 10.8 kg of pull) . Not interchangeable.