For use with SSRL Sample Storage Cassettes. The styrofoam spacer is used to keep the cassette in place when shipping a single cassette inside a dry-shipping dewar.  The spacer should be inserted inside the canister after the cassette. The Teflon canister support ring supports the shipping dewar canister preventing the handle from bending in transit. This should be placed inside the shipping dewar before the canister is inserted.