Because the chain runs in one direction, and the vessel is at the end of it rather than the beginning.
The Chain Runs One Way
Straw format determines which goblets and visotubes are compatible. Those determine cane and canister layout. Canister layout determines rack configuration and neck diameter. Which places the vessel at the end of the sequence, while its cost and lead time push it to the front of the purchase order.
What the Failure Looks Like
A straw format is selected months after goblets and canes have been bought, and does not fit. Nothing is defective, nothing is under warranty, and the tank furniture is bought again. It is not a dramatic failure, which is precisely why it keeps happening.
The Test to Apply
Every straw format in the laboratory should have a documented path to a specific canister position. If that path cannot be drawn, the organisation system has been assumed rather than designed. Standardising on fewer straw volumes removes an entire category of error. The full chain is set out in cryogenic straws, canes and goblets, with components under storage accessories.
