I have one (for sale on this forum, coincidentally). It measures approximately 10" x 5 7/8", and works on the F70, F75 and F75 LTD. I began using it on my F75 on several sites that didn't have a lot of trash, and it did slightly outperform the stock DD coil...it added an honest 1" to a maximum of 2" on bullets, buttons, and the occasional coin. What I did like a lot is that it gives a very good, solid and sweet tone on the good stuff, kind of like my old Fisher 1266x. I'm selling the 10" elliptical coil only because I sold my F75 to get a Teknetics T2 SE, since my main interest is relic hunting, and the T2 SE seemed better suited for that. If they start making a similar coil for the T2, I'll get one.
Remember that it is a concentric coil, not a DD, and consequently it did not separate targets in trash as well as the stock DD coil. Not bad at all, but not quite as good as the DD.
Low trash = 10" elliptical concentric coil
More trash = stock DD coil
Hope that helps.