The Novoflex PROLEI Balpro-1 to 35mm Format Lens Adapter Ring is the required adapter that makes it possible for the Balpro-1 to accept 35mm camera brand-specific lens adapter rings (LEI-* series). It still requires a lens adapter ring.
In addition to its function as the 35mm format adapter ring, this ring has Leica screw-mount threads (39mm). This means that lenses with Leica screw-mount threads can be used without the need for an additional adapter ring.