The Notebook Sleeve fits the Moleskin Cahier 3.5 x 5.5 paperback notebooks or the Field Notes brand notebooks or any notebook with those dimensions. The inspiration for this was from the coaches. Keeping multiple athletes numbers, notes and attempts at meets all in one place. Also meant for the person who still likes to write things down and hates big bulky wallets. Fits 2 cards along with a pocket for cash. Handmade in Los Angeles.