This new adjuster piece is a direct replacement of your existing piece. After decades of exposure to an engine compartment the original adjusters become brittle and eventually break. Even if you find a "good used" cable the adjuster piece is still aged out. While this might seem like a poor design by Mercedes it's actually a very good design. It has done very well given the materials available in the 80's. Note that any threaded screw/nut combination requires the parts to be made of the same material if they're going to last. A metal adjuster quickly wears out the plastic nut. An all metal setup wears out the stranded cable moving back and forth through the adjuster. It's all been tried. This new adjuster piece maintains their design with modern polymers and more mass.
This new piece installs in place in about 15 minutes without cutting or separating your cable in any way. The alternative is replacing the whole cable which requires either a mechanic or a longer DIY project under the car. Replacing the adjuster is 20x easier. If Mercedes offered a cable and also offered just the replacement adjuster I'd get the replacement adjuster and leave the rest of the cable alone. The adjuster lets you skip the mechanic/labor costs/down time of replacing the whole cable.
Symptoms of a bad adjuster can include the transmission appearing to slip or flare as well as late shifting or early shifting. All of these conditions will eventually cost you a transmission.
This demanding little piece has taken over a year of R&D including months spent testing over 100 design variants. After long drawn out expenses + site seller fees + PayPal transaction fees + shipping fees it's barely worth it on here because of all the middle men. If it helps I can go a bit lower without the warranty. To protect intellectual property for now the item you receive will look different from the images shown.
I did all of this to help keep these cars on the road. It would be so much easier if Mercedes would just stop discontinuing parts for our older cars but that won't change when they make more selling $2,400+ headlight assemblies for their newer cars.