I bought a Riv nut tool, see below, from this seller and when I contacted him because I broke the mandrel, by over-tightening them, on both the M6 & M10 sizes that I had bought, he replaced the mandrel for the M6 with a spare as well, and as the M10 size incorporated the mandrel in the tool (not a separate piece) he sent me a complete M10 Rivet Nut Installation Kit Attachment even though it was my fault they got broken, the M10 kit sells for £15, I don't what an M6 mandrel would cost and didn't charge me a penny, 
now that's what I call service 
http://cgi.ebay.co.uk/Rivet-Nut-Rivnut- ... 6b1b79db42
now that's what I call service http://cgi.ebay.co.uk/Rivet-Nut-Rivnut- ... 6b1b79db42
