The rail itself is of amazing quality and super happy with the product. The fittings provided however are far from ideal. Had to drill 2mm smaller hole than recommended, and the plugs still weren't snug enough (drywall). whats more, the only way to make the screws snug with this plug size, was to use actual toothpicks in each hole, otherwise the screws couldn't carry any weight at all.

Been using them for a couple of months without issues though, and they seem to hold more than the recommended 30kg per rail. 

Ideally you will need to buy a set of proper plugs for the supplied screws.