Chasing a potentially bunk Youtube video I tried out ATP AT-205 on some hard rubber parts a few days ago. Parts were the bushings between the tank and frame, one seat rubber, one engine fin rubber, and the speedometer bushings. I initially poured the AT-250 into a plastic container, and then realized I'd made a terrible mistake as the AT-205 began to take apart the container, fogging the plastic and actually causing cracks. Into a glass jar it went. 

After about 24 hours the rubber was actually rather supple and pliant again. I'm impressed. The AT-250 is a darker colour now. I feel like it might have lost a bit of it's magic eating the plastic container, but the rubber parts are still way better than they were before I put them in. No swelling, just more... rubbery. 

Remains to be seen if they just harden up again but The Internet (unreliable at best) reports that since it's mainly a plasticiser most reports are that the rubber stays in good shape afterwards.

Is it AT-250, or AT-205? 

I've used the ATP AT-205 in engines and transmissions of old cars with leaky seals and it's pretty amazing stuff.

Sorry yes, it's AT-205. I've chucked the hard front tank bushings in the jar as well as the turn signal flasher holder. It's looking brown and ugly in there and I still think the plastic did something to weaken the mixture. Might have to get another bottle for science.

Interestingly, I don't think it did much for the engine fin rubber damper I tried out. It's maybe... 20% softer than before after 24 hours. Either the mixture is weaker or that rubber is just too far gone from heat and vibration.

Thanks for confirming.