... means, in tunnel pre-support, slope stabilization , coast, mine, Structure of self-drilling bolt I. Self-drilling hollow anchor bar ... different condition, choose alloy, steel… Bit, custom design is available.(1)Diameter: R25, R32, R38, R51, T76.(2)Max. Tensile ... the accessories including anchor bits, coupling, spherical nuts, plates, and stopper. MAXDRILL Self-drilling Rock Bolt/ rock anchoring