Premium Aluminum Arm Double Mount - 4 Hole Drill Mount The only mount you’ll ever need! This heavy duty adjustable aluminum arm mount holds your Garmin Alpha 100 or Garmin Astro 430 with your Garmin DriveTrack 70. This is especially useful with the Alpha as you can see your dogs on the DriveTrack and use the tone/shock feature on the Alpha. The Drill-In is 4 hole drill in base, just as easy as the other, this screws in directly into your floorboard. .