The thickness of the rulers: 3mm, 1 Pack of 30PCS Non-Slip Adhesive Rings Ruler Grips Contains 15 Small 15 Large Rings, can be applied to the back of any ruler.
The surface of the ruler is frosted and non-slip structure, which improves the shortcomings of the ruler that is easy to slip during use.
This ruler set is fit for most low shank domestic sewing machines.