This is a mount for a Bontrager Ion or Flare RT light to fit under a specialized saddle that has the 2 threaded SWAT mount points at the back. This is
Bontrager Ion / Flare RT Mount for Specialized Saddles
Trek Bontrager Saddle, Flare R, Flare R City and Flare RT Saddle Mount - Squashyware
Bontrager Ion Pro RT/Flare RT Light Set - Trek Bikes
Bontrager Flare Round Mounting Kit - Trek Bikes
Shimano Pro Saddle / Bontrager Flare Mount (L2XNZU544) by MadBikeSkills
Lighting - Full Moon Vista Bike & Sport
under saddle tail light mounting? - The Paceline Forum
Bontrager Blendr Saddle Accessory Mount Black/Grey
For Pro Saddle Mount For Bontrager Flare Light Bracket Support Holder, Barrell Saddle
Compatibility:compatible with T rek Bontrager Ion ProRT lights, it can save more space on handlebar and provide higher security Solid and Durable
Bike Taillight Saddle Rail Mount Compatible with Bontrager Ion ProRT Headlight Adapter,Bicycle Saddle Radar Tail Light Mount with T rek
For Pro Saddle Mount For Bontrager Flare Light Bracket Support Holder, Barrell Saddle
Art Flare Rear Saddle Mount