This vernier depth gauge attachment quickly converts your standard vernier caliper into a far more useful tool. The depth gauge attachment is precision made, once clamped to the base your vernier caliper is perpendicular to the base in both directions. The base forms a bridge across the reference surface allowing the depth rod to be lowered until it reaches the lower contact point. An accurate reading of the relative height differences can then be taken. It will fit all 150mm Axminster vernier calipers and any others with a stem width of 16mm.