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Designed purely as a spare set for the P4 version of the E2 chassis in 4mm scale. Simply glue them in once cut from sprue. There are dimples on the inside of the hangars to locate 0.45mm rod easier for brake rigging.
8 are given so two can be spare.
00 & EM ones may be made available in due time. The main difference is the distance they stick away from the chassis. These can be used for 00 & EM but you will need to do a bit more clean up and save more of the sprue.
The pads no doubt could be used for other loco builds too.