If you will be bowling on different conditions, use plastic and learn a straight release. Double wood spares are exceptions. If you'll be bowling on a THS all the time, still use plastic straight for right side spares (all comments for right handed bowlers). But for left side spares use a urethane ball (I use my Slate Blue Gargoyle) and use the "wall" to give you more room for error. I target a little to the right of my strike target and, in practice, find the correct spot on the approach to stand to make the 7 pin. To make the 4, 2, and left side combinations I move the appropriate distance to the left on the approach from my 7 pin spot. The urethane reacts to the wall, but isn't jumpy like a resin ball would be. Try it, you'll like it. -- JohnP