Compare the rim and cup depth
Read the chamber dimensions without mixing them up with hose length.
Identify the measured surface
A chamber can have an outside width and a smaller usable opening. Ask the manufacturer to identify the inside rim dimensions and the depth where those numbers matter.
Separate replacement cups from kits
A compatible chamber may be sold without tubing, pump or seals. Check the full model and part number and read the contents panel.
Do not infer fit from a name
Large and petite are product labels. Compare explicit dimensions from the same part of the chamber and avoid forcing a poor fit.