i have to politely disagree with Twisty.
we thought we didn't need one on our 12' slideout.
big mistake! one year later we're having CW install one, for a lot more than it would have cost us if we had it installed before we bought our HTT.
huge difference when we camp in wooded campgrounds.
in fact, the residue from the trees/leaves actually got on the seals of the slideout and adhered to the side of the trailer.
i actually had to get a butter knife to break loose the bond it caused to get the slideout open.
in the nearly 6 years since we had it added, that has never happened again, nor have i needed to climb a ladder to sweep off the top of the slideout.
well worth the money!
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC