... bearingaircooled bearing typeFormation or layer soft ,medium soft ,hard,medium hard,very hard formationButton size (extra features)Button bit,saw teeth1) ... - 12 1/4490-78480-40mediumHard Shale, Limestone, Medium/Hard Sandstone etc.495.2~174.63 3/4-6 7 ... 8-9 1/2539-83360-40hardSandy, Shale, Quartzite, Hard Dolomite, Hard Sandstone etc.695.~-174.63 3/4-6 7/ ... Bit 165 mm with 3 1/2" REG Pin for Hard Rock