If you're after spare sensors the part numbers are TP-09S (internal valve) and TP-10S (external cap)
The Masten TP-13 (external sensors)/TP-16 (internal sensors) TPMS Tyre Pressure Monitor System is specifically designed for for those wanting to monitor their tyre pressure in a non-obscure way due to the conpact design of this monitor. .
The TPMS module simply works silently and alerts you if there is a problem with your tyres. The Tyre data can be viewed at all times.