Sturdy and not had an issue with them when I've used them previously.

These terminal blocks are made by Blue Sea Systems in America. They are not the cheapest and the jumpers seem ridiculously overpriced but the quality is unbeatable. However, it is the availability of these jumpers which makes them so very useful. Surprisingly, for something made in the U.S.A., the 30A units have metric terminal screws; M4 on the 30A blocks and M3.5 on the 20A units. Be aware that the smaller units have restricted room for the ring terminals - this is detailed on the website. As usual, the service from 12 Volt Planet is as good as it gets.

I am building a small loom for some relays just what I needed.