This kit requires a compatible BUP mount base.The Top-Center (TC) Model sits lower and closer to the saddle and is less likely to rotate under load
Horizontal Mount Arm Kit (SL) for Garmin Varia RTL510 and RTL515 (Includes Tether)
Accessories - The HIVE Bicycle Shop
Direct Mount Base for Specialized SWAT Equipped Saddles
Varia Radar Seat Post Quarter Turn Mount Compatible with Garmin Varia RTL510 RTL515 RVR315 Rearview Seatpost Clamp MTB Road Bicycle Cycling Accessories : Electronics
Specialized Bike Seat Saddle Mount for Garmin Varia & GoPro
Garmin Varia Radar Seat Rail Mount Excel Sports
Varia Mount
Trek Blendr Bike Seat Saddle Mount for Garmin Varia & GoPro
Direct Mount Base for Specialized SWAT Equipped Saddles