You're looking at a brand new deluxe Stitching Spacer, an excellent way to ensure even stitching.
Comes with a total of four stitching wheels where the points are 3mm (0.12, or 8 holes per inch), 4mm (0.16, or 6 holes per inch), 5mm (0.20, or 5 holes per inch) and 6mm (0.24, or 4 holes per inch) apart. Unlike most other kits, this one comes four stitching wheels, not three.
Ergonomically curved to maximise comfort, control and efficiency, with a finger rest half way down the neck to ensure positive control, this tool is made from steel, not cast metals, it will last years! This high quality tool is an excellent addition to your leather workshop.