keensailor said...
Don't fully understand the need for them in any case.
I have them on my boat, why? Because my wife wanted them. It was a small compromise in the sceam of things. As they say "Happy wife happy life"
They say you should leave them 'ON' all the time as it prevents groth on them. I don't, I just coat then with the clear coat from PropSpeed and give them an occasional wipe.