Des we have also a trade subscription but I prefer to use the Manos thing.
Trailers are made from galvanised steal. They are very durable. Have one since 2002 been in and out of the sea NO CORROSION
what so ever any where!! However, I wash it with fresh water every time after I put it in. This trailer is without brakes.
In fact all the trailers I've got are without brakes since the max weight on the boats (the 700RSR is just 750-850kgs and the the 640SRs are a lot less than that so no need).
To add brakes (even to those is simple enough I was told).
The calippers work with SS rods? and they do not rust. However you need to have them properly grased between the connections.
Is difficult to explain but they are not cables. Is better if you see one rather than me explaining. Is quite difficult you understand.