A mate of mine bought one of these to raise the rib on his gun to shoot DTL. He paid £235 for it. It is carbon fibre and strongly magnetic, and fits on guns with 30 to 32 inch barrels. After only using it twice, he is wanting to sell it, and buy a high ribbed gun. He is looking for £150. Here is a link to the makers web site.
http://www.highrib.co.uk/high-ribs/10mm-retrofit-high-rib