"In case you were wondering, the plug is 50mm in length.
In my opinion these plugs are not suited for M8 coach screws as they slip when tightening up in breeze block. Going down to a 9mm hole rather than the specified 10mm improves matters but ultimately it still slips. Not good with heavy loads...
No experience yet of this plug with larger sized screws but I suspect it will be better.
As of end of April 2014 the product picture shows the plug as being an Fischer S12. In fact it is an S10. This only matters if you are looking at the Fischer web site for specifications etc."