If you are wanting a nice flexible 6mm insert that is also bi-polar, take a look at this interesting insert.  This insert does have a 2.5mm input jack that works great with your Coyote Power box or any other unit that has a 2.5mm female jack on the power box.  However, if you have an E-Stim Systems 2B or any other of their units or other brands that use a 3.5mm male input jack, you can purchase a 3.5mm male to 2.5mm adapter in our Wiring and Adapters section of the web site.