General Specifications for the ALL NEW DCC27 OPTI 8Pin /21Pin Gaugemaster-Train$ave decoders:

Size: 22 mm x 16 mm x 5.mm with 1 amp continuous/ 1.8 amps maximum.

This means that they can be used for all current OO/HO locomotives as well as older locomotives with higher power needs 

Addressing: 1 and 9999, factory setting 3, 90mm Harness with an 8pin NEM 652 plug.

Harness This has a 90mm overall length. The decoder end has a removable 9 pin plug/socket, while 
the locomotive end has an 8 pin NEM652 or the standard 21Pin NEM connection.

The free purple wire is for Aux2 (Function button 2) 

The  DCC27 OPTI Gaugemaster-Train$ave decoder features:

DC Running, Back EMF, Silent Drive, 4 Functions, Light Effects, 
Consisting: The DCC27 OPTI decoders support all forms of consisting (double-heading)

Warranty:   The DCC27 OPTI Standard Decoders have a generous warranty and we encourage you to utilise it if needed.

Addressing: 1 and 9999, factory setting 3, 90mm Harness with an 8pin NEM 652 plug.

Harness This has a 90mm overall length. The decoder end has a removable 9 pin plug/socket, while 
the locomotive end has an 8 pin NEM652 plug. The free purple wire is for Aux2 (Function button 2) 

The  DCC25 OPTI Gaugemaster-Train$ave decoder features: 

DC Running, Back EMF, Silent Drive, 4 Functions, Light Effects, 
Consisting: The DCC25 OPTI decoders support all forms of consisting (double-heading) 

Warranty: The DCC 25 OPTI Standard Decoders have a generous warranty and we encourage you to utilise it if needed.