"I've used thousands of the cheapest plugs basd on cost alone. They often fail and never suit very tight requirements. I chose to test out a few expensive wall plugs. These plugs, though more expensive are not the most expensive but perform excellently. Smaller than the cheapest, I've yet to have one fail. These are better than the more expensive Fischer & Mungo plugs. I use this size 4-6mm as a 7mm hole replacement all the time."
"when you buy the fischer plugs you get less than you wanted as the first 8-10mm don't catch the screw. these rawlplugs grip right from the start but these bigger sizes:brown and blue: should be longer, at least 35mm as they are meant to take heavier loads and as they are they'll hardly penetrate the rendering coat"