u/This_Foundation_3444

I was directed here from the succulents community to ask about grit size. I've purchased hardy ice plants to place outdoors on a small retaining wall. I was going to use a 2-4 mm crushed granite with some pumice but was not sure if I should use 6 mm or 3 mm pumice? Or does it not matter? I live in Easter Pa so I need well draining soil for the fall, winter and spring Any help or advice would be appreciated

Thank you