Python Rope Cinch

[legalfee]

Anyone use some of these?

 

[GA_Boater]

Not here, but 50 bucks each is a lotta gas money to hold a fender line. My view on this doesn't mean you shouldn't try 'em out.

 

[Scott Danforth]

this is free. https://www.animatedknots.com/bowline-knot

 

[HotTommy]

Short answer: no.
Longer answer: I've used cam cleats on my sailboat to rapidly and securely hold sail lines and I like them. They seem to run $20-30 on average, but must be mounted in one place. A cam cinch for a fender line seems like overkill to me, but maybe you need to adjust the height of your fenders more often than me.