Good information. I use 60 mm and to get straight of grain I fold fabric then line up the bottom folded edge on the bottom of the cutting mat, then using the lines on the cutting mat line up a ruler to make your first cut on a straight line sliding the ruler towards the cutting edge then cut across the fold to the open edge. You might lose an inch of fabtic to get a straight line, If i need 2 inch pieces I cut 6 inches then slide the ruler to the 4 then 2 this keeps the fabric together and you get more cuts without lifting the ruler or fabric. Hope this makes sense. Use the mat and your ruler as a cutting guide.