What are they?
How much of a difference do they make?

We've had the same kickbacks for about 30 years at the house I'm at, they just changed them with "new for us" kickbacks.   What should I now expect?  My team bowled a 3360 scratch last night which beat our teams previous high of 3260 for the year.  

Thanks
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High game 300
High series 804
High triplicate 774
High average 221
best game. when I was 6 I bowled a 158