After our in-house comparison of Fotodiox Pro PRONTO Adapter - Leica M Mount Lens to Sony E-Mount Camera Autofocus Adapter and the Techart PRO Leica M – Sony E Autofocus Adapter we see minimal difference in the real world performance between the two units. As always, we recommend assessing your needs to determine what is best for you. Below you will find the differences that we have observed.The main differences are price point and warranty. The TechArt Pro adapter currently sells for $379 and comes with a one year warranty, whereas the Fotodiox Pro Pronto adapter is currently selling for $329.95 and comes with a two year warranty.As for the tech specs on the items the only difference that is of note is the weight bearing tolerance of the adapters; the Fotodiox adapter will safely support a lens up to 680g(approx. 23.98oz) and the Techart will support up to 700g(approx. 24.69oz). It is possible to use a heavier lens with a foot and let the adapter support your camera as long as your camera falls below these weight tolerances.The focus ability of both of these adapters relies on heavily on a manual approximate focus and the use of phase-detection autofocus. These adapters were designed with the use of phase-detction autofocus in mind. While you may be able to achieve some success with contrast detection auto-focus, our test show that at best these results will be inconsistent.It is also worth noting that this adapter can be used with many other Leica-M mount manual adapters to double adapt lenses from other systems to provide auto focus to a wide variety of vintage optics.