The yellow part is like slime, and it's non-slip, so the sheets won't slip. It separates into parts. You can use it as your child grows. The grooves are quite deep, so you don't have to worry about urine leakage. It's used, but the condition is very good, and it's very clean, so it hasn't been used for very long. Thank you! (^-^) Wide size Sometimes, regular size