Hornby HC8040 Scharfenberg NEM couplings - pack of four
Scharfenberg couplings are one of the most commonly used type of couplings on modern trains across the UK and Europe. Designed to make electrical and pneumatic connections automatically and smoothly, these couplings can be substituted for the NEM couplings supplied with models for a more authentic and accurate representation of the original. These couplings create a closer and more realistic connection between units, therefore it is recommended that you check your DMUs and EMUs are suitable to accommodate the couplings effectively as they may not be suitable for UK stock without the extension of the NEM pocket.
More information on the couplings can be found here:
http://en.wikipedia.org/wiki/Railway_coupling#Scharfenberg_coupler