Scale Size HO Couplers

[torikoos]

The cars that I just got today, all have the scale size couplers and they will couple just fine with the Kadee No. 5's, but I have noticed that they don't couple to each other as reliably as cars with the No. 5's.

It does depend on the manufacturer. In my experience, Kadee still can't be beaten on quality and reliability. I've found several other brands, particularly those that use molded on plastic springs to be unreliable. They're usually too stiff (finding plastic flash on them quite often) and either don't open, or stay open, and when coupling are being pushed sideways instead of the knuckle opening up. This is particularly true in a bend, when cars are not perfectly straight. Kadee couplers suffer from this far, far less, they are a bit more expensive, but you get what you pay for. So even those that come with knuckle couplers (scale or not) I end up changing out for Kadee eventually. (tricky sometimes, springs, washers etc needed here and there).
The fact that they do couple with the no 5's as you mention is probably thanks to the light and smooth action of the Kadees, rather than the scale coupler of mfg X.

Good luck

Koos