BASIC GREY-Magnetic Precision Mat will take your next trimming task to the highest level of accuracy. The 15x15 self healing mat is accompanied by an 18 magnetic stainless steel beveled ruler and eight super-strong magnetic tacks. The mat has a perimeter that is marked every 1/8 and an interior marked every 1/2-both with an easy to see white true-sized grid. Magnetic attraction makes trimming easy and precise while you explore unlimited design options before making a project permanent. Magnetic Tack Refills are also available.