Perfect sizes for what I was hoping for.  The problem is the sealing top.  When I push the top down to seal it, it eventually unseals and moves back up and so it won't completely seal the canister.  I am not sure how to deal with this.  I have tried to re-seal it by twisting the top down and it stays for a while and then when I come back to check on it, the top has lifted up again, so it "un-seals" itself.  Any suggestions?