My 17x24 (x 1/2 inch) 100% gray wool mat is from Wooly Felted Wonders. I use it with a clapper and wouldn't part with either for any reason. Piecing looks so crisp and a finished quilt looks so awesome. I purchased mine at a quilt shop but they can be found online at woolyfeltedwonders.com. Very much worth the money. I wouldn't advise a smaller size.