I have a Martelli round ratating mat which I love but when I went to trim out 100's of blocks recently, they kept slipping so I used 505 spray to keep them where I needed them to be so now it's all sort of gummy. I used the spray I have to get the gummy crude off my embroidery hoops but it doesn't work quite as well. Just about that time, Martelli was having a sale on their rotating mats and parts so I ordered another cutting mat top only to have on hand. I'll use the crudey one when I need to spray 505 to keep them in place and the good one when I don't. Yes, they're expensive even on sale but I love Martelli products and always look for when they're having a sale to order.