Tree and shrub auger bits from Manitou are approximately 1 250 mm in overall length, 5/16 inch double wrapped auger flighting and has been designed with smaller diameter at the bottom. This innovative design leaves space for root balls, fertilizer, or mulch. Tree and Shrub auger bits have Tree and shrub auger bits from Manitou are approximately 1 250 mm in overall length, 5/16 inch double wrapped auger flighting and has been designed with smaller diameter at the bottom. This innovative design leaves space for root balls, fertilizer, or mulch. Tree and Shrub auger bits have heat treated teeth and a "fishtail" centre point. and a "fishtail" centre point.