Re: keel roller
Those caps are not reusable, I usually just clip the edge with a pair of wire cutters and peel them off. New ones are only spare change at the marina.
I think the last time I bought them they were like $.25 each or so for galvanized.
I like to use Urethane or PVC rollers, they don't mar the boat like old fashioned rubber used to. There a bit more money but they last pretty much forever.
Many new trailers now come with the PVC type rollers.
Top of the line is probably Stoltz brand polyurethane rollers, (the clear/gold colored rollers. I generally use rubber for the keel rollers and PVC for my bunk rollers. I'm not usually very concerned about marking my boats up and keel rollers aren't as big of an offender when it comes to leaving marks on the boat.