The theory for using a plastic spare ball for all spares (not just 7 pins or 10 pins) is to take the vagaries of where is the oil and where is the dry and how much should I hook it, should I hook it and where should I throw my striek ball to make this or that spare. The harder the plastic ball, the less it will hook. The less it hooks the closer your spare release can be to your strike release and the less you need to worry about where to throw your spare ball. Some of the very hardest plastic balls, like the Columbia Blue Dot and Storm's Spare Storm (that is what it is called) can be used very easily.

(New Blue Dots are not as hard as the original; due to lack of demand, abut a year ago or so, Columbia started making them the same hardeness as their White Dot. So, I believe the Spare Storm is now one of th ehardest plastic balls made; the Roto-Grip Cosmos is also very hard. See the manufacturers's websites for the actual hardness of these balls.)

All plastic balls will hook more as they track out and get worn; the harder they are, the longer they will take to track out. They are also very easy to resurface and polish to a high gloss; as such, they will go straighter.

That said, some people have slighter harder time than others in getting used to throwing a straight ball at spares. However, it is well worth the effort. Plastic balls are cheap, much cheaper than resin and particle balls.

Buy one and try it out and practice with a plastic ball in order to get used to it both mentally and physically. It can be and should be used for all spares.

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"Just because you can do something does not mean you should do it."