Whats up guys, just picked up a turbonetics ball bearing T4, theres one number on it and im not 100% what turbo it is. How can i tell which turbo i have?

Heres a couple pics:

 

Take the covers off and measure the inducer and exducer wheels.

 

If i take the covers off wont i have to get the turbo rebalanced?

 

no

 

And when you measure, you'll need something more precise than a simple tape measure or ruler...find a micrometer/caliper to measure it properly. Small differences in turbos make a big difference in characteristics