There is a chamfer on the cylinder and you can squeeze
them in with your fingers but this is what I use. Not
expensive but if you search around some you may find
a better price
Tubs
https://www.ebay.com/itm/174782484640?epid=3047086852&hash=item28b1d910a0:g:p68AAOSwjatgrlZz.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.