Selection of surfaces withing another surface

Hello everyone,

I have a definition and I have stacked at a point where I want to keep only the spheres which are completely within my arches surface.
Can anyone help how to do this?

Alexandros (11.7 KB)

Try that: (14.0 KB)

Thank you Michael.
Works perfectly.

Hello Xade,

Of course if I have the knowledge I am glad to assist you.