You can also use an xacto blade to carefully score the teflon insulation and then pinch it between your fingernails and pull it off. a bit tedious, but perfectly workable if you only have a small number of wires to do.
I've got a set of Klein standard wire strippers and I've never had a problem with the Alpha Teflon wire. Someday I'll find an excuse to upgrade to the style PB recommended.
After reading this post I realised I did the speedball upgrade with all the wires from the crack which is a lot thicker... Im happy to report it works and no issues so far.
The wire we provide with the Speedball kit cannot be melted or burned with a soldering iron, and this can come in really handy with the installation of the Speedball.