Before you you buy it be sure you need it as this ain't like trying on shoes. You install it, you bought it.
Testing coils for resistance is a fair way to test, but the best way is dynamically with an engine secondary ignition oscilliscope. By openning the circuit total available voltage can be read.
We see many more of the new short coils going bad than the old tall round coils.
Bosch Master, ASE Master, L1
33 years MB technician