Often times balls aren't too enthusiastic about those because they're open on both ends. He may like it better if you close off one end of the hide. Also, your snake shouldn't have to choose between thermoregulating (because he's cold-blooded and uses outside temperature to maintain body temperature) and feeling secure, so it's best to have good, secure hides on both the warm side and cool side of the enclosure. Hides can be as simple as a terra cotta flowerpot turned upside down with a hole knocked in the bottom edge and smoothed, or rocks cleaned (with bleach water) and carefully, securely stacked to create a hide spot, or a piece of cork bark lying on the substrate, or a cave made with papier mache or clay. There are lots of things that make good hides. The primary things to consider are 1) is it safe for the snake, 2) is it secure, with just one entrance and not too big of one, 3) is it snug when the snake is curled up, and 4) does it have some heft to it, making it feel more like a naturally occurring hide like a burrow or crevice. If you can answer yes to all 4 of those, it should make a good hide.