New Hydrostar Drain Monster Drain Cleaner 4 Piece Bit/Cutter Set. You will find this set to be a much better set than what the Hydrostar came with. If you need the metric screw that holds the bits onto your cable end, the size is (M6 X 1) or you can simply tap the cable end to (1/4 - 20) and use a standard 1/4" coarse thread bolt. Both are very close in size.