Removing a rotten plumbing vent boot and replacing with a new sleeve made for this very application. 

I inspect my roof every year first place to crack and deteriorate is the lip of those rubber tubes i use silicon on the inside and outside for extra protection it will make it last longer to maybe 5 years vs replacing it every year for the lip failure Some will say u need to have a place for the water to escape - yes it is the bottom of the plate

The replacement Vent Collar Manufacturer recommends to slide another vent collar over to use as a 'sacrficial lamb'.

I saw another video where they just(it was an oatey rubber boot) cleaned the silicon off the old one, applied some lap caulk, and slipped the new one over the old one....your approach looks cleaner for sure but the other technique is an option I think.

Is it really necessary to caulk around the rubber?

Where did you get the boot? It looks like a Water Tite roof jack. Will the Oatey replacement boot also work? Thanks

haha never seen a Stanley Wonder Bar used in that fashion

Hey, what size vent pipe was that.

I think it will hold!!! I hope so..

You need to replace the vent not just the seal.