Typically the rubberized horse hair is not the one that disintegrates its the none treated horse hair. What you do is find a 115 114 at a pick a pull and slice the skins off and remove the padding and see what it is....the 123 pads may also work. Removing the skins are simple, sometimes a little tricky....the skins are held into channels on the seat frames, with cardboard strips that are sewn onto the skins. You have to take the seat out, take the back off....flip the bottom and press the springs down and work the cardboard strips out of the channels with a regular screw driver.

Here's a link with a few photos of a w123 bottom skin removal
swapping MB-tex skin on 123 seats

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