TamSeal TG66 is an economical driving grade tail sealant for shielded tunnel boring machines (TBM). TamSeal TG66 has been especially designed for use in less challanging ground conditions and profiles. Together with the wire brushes, the sealant forms an impermeable barrier between the tail shield of the TBM and the concrete segments to effectively seal off any ingress of water, soils and annulus grout/mortar grout back into the TBM invert.