"Rawlplug have made these things seemingly since forever, and they are still one of the best for ensuring a solid fixing that allows the bolt to be removed/refitted over and over again.
Warning! If over torqued, are likely to crack or split the substrate they are in! So really, don't over tighten (esp. when into bricks). They also need the larger hole into the substrate first, so can't be drilled straight though (As with some other fixings.)
Another drawback with the M8 and above sizes is:- They need a large hole size (14mm and above), which should be a concern for many DIY'er's as most hand and battery drills chucks, won't accept this size bit (They usually only accept up to 10mm or rarely, a maximum of 13mm). I haven't yet found such a drill bit with a reduced shank (Other than maybe by using an SDS bit in a standard chuck! (Not recommended!)).
But still, installation drawbacks aside, they're a truly powerful and reliable fixing system."