Thera-Band Light Flex Bar Exercise Equipment to Relieve Tennis Elbow For the relief of tennis elbow 12" long and is made from dry natural rubber in 4 progressive resistance levels to match user capability The Yellow TheraBand FlexBar takes 6 lb. of force to bend to a u-shape, Red 10 lb., Green 15 lb., and Blue 25 lb. Diameter: yellow = 1 3/8", red = 1 1/2", green = 1 3/4", blue = 2"