CRAIN 502 EXTENSION TUBEEach No. 502 Extension Tube Section can add up to 4 feet 8 inches of length to your stretcher in 4 inch increments. The holes of the tubes are punched rather than drilled for precision and durability. The spring buttons are flat on their top faces for smooth adjustment. The buttons are precisely located within the inner tube, so that they retain hold the outer tube on the inner tube during transport. Works with other standard size diameter poles.