Even though the spelling is the same, not all evaporators are equal. From the same supplier I can purchase 124 evaporators from $89 to around $230. I usually buy the $230 one.
It is an exact replacement including expansion valve and the insulative boot where the hoses go through the case. I have used many of the copper units (the cheapest) but can not stand to deal with the crummy fit. The aluminum units with expansion valves fit and look exactly like the one from MB. Hopefullly they have improved the metallurgy.
Bosch Master, ASE Master, L1
33 years MB technician