The KK133 is a great capsule, but it's *NOT* a nickel membrane.
If you want a nickel membrane you need to get the Gefell M221, as Neumann Berlin cannot make nickel diaphragms ;-)
The KK133 has a *titanium* membrane.
The KK133 is a *very* nice capsule - it's basically the same capsule that was used for the M150 and TLM50, but with the KK133 you have the option of using it without the sphere.
The KK133 is great for a Decca Tree, it gives the same response as the M150 / TLM50 but slightly better as it's in a smaller housing without the large metal screen. It's also very much lighter and a great choice.