The Gallery System Adjustable Hooks have been around for many years and represent an excellent hook solution at an economy price. They are particularly good where regular adjustment is less likely. They are adjustable with an included allen key and are capable of holding 20kg per hook (15kg on the Clear Tape Droppers).
Things to consider
The Gallery System Adjustable Hooks are designed to work with both the Clear Tape and Stainless Steel Dropper Kits.
The hook has been cleverly designed with a broad flat back, minimising the chance of any wall bruising if it became stuck between the piece suspended and the wall; not that this is likely as it is quite thin. You will note that the hooking point and the dropper touch minimising any forward lean effect due to the hook.