[TowerTalk] No end caps

[K4SAV]

I would like some suggestions for a material to use for plugging the 
ends of booms and antenna elements to keep the critters out.  I don't 
like using caps because those just trap the water inside.  I have tried 
plastic pot scrubbers.  Those work well for a while until the UV gets 
them.  I tried the copper pot scrubbers and it turns out they are only 
copper plated and they rust in a short while.  Other suggestions?

Jerry, K4SAV