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5850 9.5 inches took me seconds to find this out,not hard really tbh is it?
4850 9 inches
Best thing to do is check the manufacturers webpage of the card you're looking at. You'll get the measurements there.
Dimensions: 260x100x33 mm or 25.7 cm x 10.6 cm x 3.6 cm
2 different sizes for the ref 1 sapphire after a google search for ' sapphire 5850 dimensions '. They're similar enough though.
" the HD 5850 comes in 9.5" (24cm) which is the same as the HD 4890 "
http://www.tweaktown.com/reviews/2947/sapphire_radeon_hd_5850_1gb_video_card/index3.html
Keep in mind that the pci-e power connectors on the 5850 are on the end of the card, facing the hdd bays in a case. If you're really tight for room, getting the power connectors on as well might be a struggle.