The Moore & Wright 891 Series Adjustable Depth Micrometer feature interchangeable depth rods, with a 4mm diameter.

These adjustable depth micrometer's conform to BS6468:1984.

Base Length: 63.5mm / 2 1/2in.

The Moore & Wright 891M150 Adjustable Depth Micrometer has the following specification:

Range: 0-150mm.
Resolution: 0.01mm.