bumGenius's most absorbent insert! bumGenius One-Size Microfiber inserts are made of 3 layers of the thickest microfiber terry available anywhere. Our unique snap down design allows these stuffable inserts to fit perfectly in our bumGenius 4.0 One-Size Stay-Dry Cloth Diaper. Our new, wider and longer design fills up these diapers side-to-side and end-to-end. No more leaks! The One-Size Stay-Dry Insert measures 15.75 x 5.5 inches.