Did you mean RSL29?Not sure, but not the ceramics. I should definitely have replaced the rotors at the time, they had a kind of uneven surface developing. The back breaks i had to take to the independent mechanic and had the hawk pads installed and they work fine. I was going to get these race pads called pagid rs29 but they are quite expensive and you have to front and back at the same time or just the fronts would throw off the balance.
Did you call about fittment? THey don;t list the GLA, though they list the A-45 and CLA-45 (don't say sport brakes or not for CLA). They also list the SLK 55 AMG 2012+, which Ebay seems to say compatible.
That's size 8188 for the front. and 8189 for the rear.
In 8188 they have RSL 1, RSL 29, and RS 14
In 8189 they have RSL 29 only.
I'm not sure why you could go RS14 in the front and RSL 29 in the rear, but not go RSL 29 in front and OEM in the rear? If you have to match compound, why would the fronts be available in more compounds? The SLK 55 AMG would have the same problem as us.