As a rule of thumb, In-runners are lower voltage and Higher KV and Out-runners are lower KV and Higher Voltage.

In-runners go up to about 8S max voltage where as a Out-runner will take 12S. However, In-runners can go as high as 5000Kv+ where as most Out-runners do 500-1000kv, only 10-20% of the In-runners.

This all of course depends upon their size. Scorpion have a HK-25 that does 3500kv, and a Turnigy 1015 can do 11'500KV. On the other end I have seen a liquid cooled in-runner as low as 620Kv and a Our-runner at a mere 168kv!

This has been Roseanne, your guide to the world of facts.