As I understand it Spartite does both Keep the mast from moving in the partners, and keep the water out. You skeptics can keep wondering why your rubber boot leaks
when your mast is moving around in the partners. The spartight motto is "Spartite keeps the mast up and the water out" It could be compared to putting a cork back in the bottle or covering it with saran wrap.
I just love how when I post that it has worked for me for 16 years, people who have never used it post how it can't possibly keep the water out. I've been in the marine
business all my life and have never heard of anyone not happy with spartite. But most users are racers because most cruisers are to cheap
to buy it.
When someone ask a question it would be nice if people didn't respond "as I understand it" without firsthand knowledge. I'm going to unsubcribe to this link now and hopefully OP will have checked out the spartite website for himself.