I also bought a set for 255-525 hangers but the center web was pretty thin and the rubber pretty soft. Didn't think they'd last very long.
Removed my frame mounted hangers and redrilled them to line up up with the sidepipe hangers.
I use Bosal 255-481 thru Rockauto. $1.37 each. I also wrap the rubber isolator with a hose clamp just barely tight enough to keep the clamp from walking to act as a reinforcement of the rubber.
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Or you can buy them thru Back Draft $11.99 each.
Backdraft Parts - Exhaust Hanger Rubber - Exhaust - Products