I have used the tx4600 fitted to quadbikes for hunting and mustering and find them to be very suited to the application.Buttons on the handpiece make changing channels easy while in motion. IP67 rating means the unit has total protection to dust causing a malfunction and can be immersed in water 15cm to 100cm deep without malfunction - is totally suited to outdoor use even in heavy rain or dust. I dont think i would immerse it in water though. Loud speaker (aiming the unit at you makes it much louder) makes it quite easy to hear when riding a quadbike even at speed. A little more expensie than units with a lower or no IP rating but for bikes, tractors and the like it is totally worth the money.
Loud speaker, compact unit, IP rating.