Rockcare Framus Fret Protector 6

I'm perhaps not using it for its intended purpose, but it works for me: I install under the strings every time I use a string conditioner/cleaner to avoid contamination of the fretboard. I prefer to use fretboard conditioner and cleaners on the fretboard and to avoid soaking it in something intended for strings - and some string products seem to dispense very liberal amounts of oils every now and then