[DmaxDually]

I have the 507 with the flow thru sensors on my Dually and now on my Monty with brand new G614's. You can get the batteries (CR1632)for the sensors on eBay for under 4.00 for a pack of 20 including shipping. I like the flow thru because they don't have to be removed to air up and I can replace the batteries. I don't have to by a new sensor or have the tire broken down when the battery goes dead or I have a problem with the sensor.

A word of caution or advice from experience....Do not put the sensors on rubber valve stems not even the rubber high pressure stems.. Have your valve stems replaced with metal bolt on stems. About several months after I first installed the sensors on my dually I got a flat because of valve stem failure. The valve stem failed right at the point where it comes thru the rim. The following statement is from the manufactures(Truck Systems Technologies) website FAQ's:

Do I need special valve stems?
No, you do not need special valve stems, but you do need commonly available metal valve stems.

I really like the system and it works great.