Stripping the main gear typically requires sudden stop of the blades. I have a CP Pro 2, MSR, MCX from E-Flite and a couple of HK450. I have only stripped the main gear a couple of times on the CP Pro 2, and a few times on the HK 450s due to either crash of blade impact. Main shaft (if it's like the CP Pro 2, the main gear comes with shaft) and spindle are also good things to have.