Each panel consists of a drum-type continuous miner and a multiunit, mobile chain conveyor system. The haulage system consists of three 7.6 m (25 ft) long, crawler-mounted mobile conveyor units with three 12.2-m- (40-ft-) long bridge conveyor units piggybacked onto the mobile units. Each of the six components has separate conveyor chains, but they are pinned together at transfer points. The unit closest to the miner is the "hopper" mobile unit, which is physically detached from the conveyor discharge boom of the continuous miner. The final bridge conveyor is pinned to a dolly that rolls on rhe panel belt structure frame. This frame is typically about 67 m (220 ft) long and includes the panel belt tailpiece. The tailpiece gives the haulage system the capability of backing alongside the panel belt . When fully extended, the haulage system reaches about 61 m (200 ft) from the panel belt.