The ROK 550T is the second model in the Rockmore International T-Series DTH Hammer line. The hammers use drill bits with standard shank connections without plastic blow tubes/foot valves. The 5-inch class model and tubeless hammer accepts the industry standard bit shank model QL50, but with the blow tube/foot valve removed. Rockmore International says there are economic advantages of eliminating the traditional plastic components from the bit shank section; blow tube/foot-valve breakages on DTH bits during drilling operations immediately cause the hammer to stop functioning. This can be especially harmful for drill time efficiency if such interruptions occur in deep-hole applications, requiring the hammer to be retrieved out of the hole for bit replacement.