Each block/pack includes 2, 4 or 6 ignition coils combined into a single unit. HT leads are used to connect the outlets of the block coil to the spark plugs. Block coils feed voltage to either one or two cylinders simultaneously. Used in modern systems with no distributor.
Dual Spark Ignition Coil (ignition coil with with wasted spark design ).

(1)Double Spark Ignition Coils 2*2 for Four Cylinders
Double spark ignition coil, for 2 x 2 spark plugs. For example: Volkswagen ignition coil

(3)Double spark ignition coils 3*2 for six cylinders

Coil-No-Plug ignition coil with wasted spark design

Ignition coils (Coil-No-Plug ignition coil with wasted spark design) are mounted on the spark plugs for cylinders2, 4 and 6. Take Mercedes-Ben M104 as example (Mercedes-Ben ignition coil M104 with wasted spark design)

The ignition system is often used in economical cars with low-emission. 

When the ignition coil is in operation, both cylinders fire simultaneously. Only one cylinder does intake stroke and the other is exhaust stroke.