marshall is coming out with a gps unit sometime next year and i heard its alot better than garmin but i have a quick track 6000 and rebuilt collars by mike rivers and it works good i dont over lap the numbers i have 4 of them 216.766 217.104 217.198 217.827 and i thought i might have a problem with 104 and 198 and actually i dont and it reaches 4 miles in my cedar swamps