I bought a filter and volume off ebay and I asked before buying if it would work in my bass and the seller said yep. I went to upgrade it with a 3 way Q switch and it wasn't working properly. I sent it in and it turned out to be a lowpass guitar filter. It's kind of stressful because I only bought from ebay because I am on disability and I was trying to save. The seller has another filter up and I am guessing it is another guitar filter

Is a guitar filter that different from a bass filter?

I've always thought they were the same.   It's also been my experience that, on a guitar, the usable portion of the sweep is quite narrow, sort of like everything happens between 4-6. 

Bill, tgo