This isolator switch is handy for large electric airplanes and a great convenience for mid-sized electrics.
Simply install the receptacle to the fuselage side and connect the battery and ESC.
Plug or unplug the connector key to turn the power on and off.
Compatible with Ultra Deans connector.
This high current version has heavy duty 12 gauge wire.
This comes in handy since some batteries mount from the bottom on some models.
It's also good as it adds another level of safety to electric models during busy times at the field.
It is handy also when converting an IC model to electric.
When it's time to fly, you simply turn on the transmitter and plug in the arming switch.

It is available from a US based internet store, parkrcmodels.com/ at around $12.99 each plus postage (they also accept Paypal)
It is from mpi Maxx Products International (MPI).
Spare plugs are also sold separately for around $3.95 each.
It works out best value when you buy 3 pcs when you account for postage.
It may also be available in a local shop.

Cheers John Kalaitzakis.