Reddit reviews Top Flight Clasp Envelopes, Gummed and Clasped Closure, 10 x 13 Inches, Brown Kraft, 8 Envelopes per Pack (6911068)

My own current storage solution consist of two core boxes cut and taped together. I followed this guide here. It's reached it maximum capacity at the moment with 2 core sets and all of the Dunwich and Carcosa cycles. If I plan on getting The Forgotten age I'll have to retire it.

As for the rule inserts, I keep those in a separate brown office manila envelope. I unfold the heavily folded mytho pack inserts, then flatten them out and they all fit in a single envelope fairly easily.