Thanks, just ordered from tsttruck.com. 4 wheel system for $199
Looked at Tsttruck.com and found this interesting:
507 set up for two wheels = $99 ( Includes monitor / power line / mount & 2 sending units.
507 sending units = 2 for $100
TOTAL for 4 wheel monitoring = $199
If you buy 2 of the 507 two wheel units ( 2 monitors / 2 power lines / 2 mounts & 4 sending units = $198
It seems that the monitors & their parts are the cheap end of the system.......Maybe I'll just buy 2 systems, save a buck, and have a spare monitor if there should be a problem