They are glued in. Give it a good visual inspection for any bad spots. If it looks OK and is still soft it should be sealing OK. About the only way to get them out is to destroy them. Pull out as much as you can, then I use a flat blade screwdriver about the width of the channel to scrape the rest of the junk out of the seating grooves. Takes some effort and time. Now comes the debatable part. Hayward recommends crazy glue...at least they did last time I looked a couple years ago. Tried that once and didn't hold too well. Last year, pulled it out and squished silicone seal in the channels and used that as the adhesive. Prepped a circular piece of plastic sheeting to fit over the gasket. Wanted to reassemble the valve and put pressure on the gasket before and during the silicone curing process. I waxed one side of the plastic sheet so the silicone wouldn't stick to it. Can probably use wax paper too...just thought of that. For the first few hours I'd move the handle to a different position so all the webs of the gasket get pressed into place. After curing, a day, take the valve apart, remove the plastic or wax paper, trim any excess silicone seal out of the channels and bingo. I always have had a slight leak to waste but since I did this, nothing. A year now. There are people that suggest not gluing it at all. Can't understand the logic here but won't argue. This is what worked for me.
Al

(ajs-1)
In case you wonder what this is, on some posts that I want to find in the future I embed a unique search field.