When used with their DVDWS, DVWS or WS counterweight systems, this Losmandy 2.5-lb Counterweight allows you to properly balance your OTA and accessories on a mount. It can be used alone or stacked with other weights to relieve stress on the mount's gears, which makes it easier to move for smooth tracking. The center bore hole is threaded to fit the system's counterweight shaft and allows the weight to be set into position anywhere along the shaft for precision balancing.