Dexcom G4 Professional User Manual page 22

Acoustic spacer Triangle seal
Square seals Receiver shield
Receiver shield pack
The receiver shield and components are disposable and must be
replaced with each individual patient's use. The receiver shield and
seals are used to help protect the receiver from contamination. The
acoustic spacer is used to ensure the alert and alarm sounds are still
audible when the receiver shield is over the receiver.
Dexcom G4 PLATINUM Professional System User's Guide | 21