I'm not sure what a Cobra is... so I'll stick this post here thinking it is arguably a Feather blade holder with the handle misplaced.
Turtle and Bluebriz were talking about their Cobras in another thread and I decided to find one... and, as usual, someone was more than happy to fulfill my acquisition disorder.
My first shave was fine but I, like many others, was confused about the handle design. The angle could be figured out but the handle just didn't make sense (to me). The front with the knurling was fine, the back with the ultra smooth surface was a hazard in my hands. It was annoyingly slippery. So... never one to let a good design go unpunished, I decided to modify it just a little.
I used some non-skid tape - similar to what the gun/pistol owners use for Glocks and such - and put it on the back. Now, at least, it has grip. The tape works fine - I used it on another razor - a 'Western Kami' that had a really slippery handle. It fixed it perfectly. The tape is waterproof but can be removed/replaced. FWIW - I have some on a Glock that I have used for several years and it hasn't had to be replaced so I think it should last a while.