This Tripod Mount Ring from Tamron is for their SP 150-600mm f/5-6.3 Di VC USD lens. This is an optional accessory to replace the shorter tripod mount ring that is included with the lens. This ring has an extended base surface and a second mounting thread for a more secure mount. The larger base has knurled finger grooves, making it easier to hold and carry the lens.
UPC: 725211011057