A sub used to enlarge and undergauge well to gauge, ream out ledges and split casing, remove key seats, and straighten a well. It has cutting blades, rollers, or cones of tungsten carbide on it and is run down the well on a drillstring.
Griffith standard three point roller reamers are of heavy duty design utilising drive fit hardened reamer pin blocks which can be easily field replaced by rig crews.