(Hetherington), Pile Driver (Skid or Crawler), Road Paving . Mixer, Rock Drill Crawler or Skid Rig, Rock Drill (truck . Mounted), Ross Carrier, Roto Mill Grinder (36"" and over), Roto mill grinder (less than 36""), Throttle Valve and . Compressor or Clever Brooks Type Combination, Throttle . Valve and Fireman Combination or Horizontal or Upright