The MS Optics 28mm f2 Pancake lens offering is a lens that should be permanently glued to a Leica CL if you have one. Now, don’t go doing that for real now, but more to the point, this is a lens that really should be glued on. Why? It’s incredibly small. The MS Optics 28mm f2 is one of the smallest lens offerings for the Leica M mount, with perhaps only Lomography’s Minitar 32mm f2.8 lens rivaling it. In fact, both of those lenses have unique image qualities to them as well as drastically different price points. Their operation is quite similar though due to their being this small.
One thing is for absolutely certain: mate the MS Optics 28mm f2 to your Leica M mount (or any M mount camera) and the package will be that much lighter and smaller than nearly any other lens you use with your camera.