Made from drop forged steel in one piece.

Head and adjustable cutters hardened and tempered.
Locking screw zinc plated with hexagonal head with slot.

With expansive bits it is possible to drill a full range of diameters with the same bit, in wood.

Adjustable with screwdriver or wrench.

Size. 15-45mm.
Length. 120mm.
Shank. Round.