This is the EZ Tail Light Series bracket.
Fits seatpost and seat stays up to 32mm
Base (mounting parts): The hard material makes it easy to install and remove the light. Even with gloves on, you can remove the light without removing the silicone band. The base can be installed in addition to the included silicone band and the commercially available O-rings.
Short Silicone Band: The ladder-shaped silicone band is compatible with standard seat posts (1.0 - 1.3 inches (25 - 32 mm) and seat stays.