75 Foot Thomas Racing Lane Line With 4 Inch Disk Thomas Sports 40075000 40075000 The design of the TSP 4 Inch Racing Lane allows waves to be dispersed along the channel of revolving disks. This helps maximize control of the water surface, especially important for competitive swimming.Every lane is constructed of 4 inch plastic disks and donuts that are strung on vinyl-coated 3/16 inch stainless steel cable. The disks rotate independently of each other, so as a swimmer creates a wake in the pool, the lines absorb and distribute the energy efficiently. This construction also helps to quell waves from one lane to another.Racing lanes attach to the pool wall with a stainless steel tension spring at one end and a stainless steel ratchet at the other end. This allows the tension to be customized based on the needs for that specific event.