If you are looking for reliable automatic couplings for your model trains take a look at Kadee couplings.
The couplings are not intrusive and are very reliable. Kadee couplings have delayed action. This means that you can uncouple a wagon above the magnet and then shunt it without it coupling again.
The numbers 17, 18, 19 and 20 are especially designed for NEM pockets for HO / OO. These models are in 4 different lengths.
The reliable No 5 coupling and the other types are also for HO but for rolling stock without NEM pocket.