Features: brand new and high quality Made of Aviation Aluminum CNC precisely machined, hand-polished, anodized surface with non-slip rubber and 1/4" stainless steel screw and spring; Inner diameter is about 76mm, width is about 18mm; Split-structure, bottom with quick-release plate design, the plate's length is about 55mm, with 1/4" and 3/8" screw holes; Replaces the original tripod mount base of Tamron 18-400mm F3.5-6.3 Di II VC HLD B028 lens, The bottom is quick release plate of RRS standard interface, for RRS / KIRK / WIMBERLEY / MARKINS / SUNWAYFOTO / KANGRINPOCHE / BENRO / MARSACE ball for head Package Includes: 1 x Lens Tripod Mount Ring Base IS-TA1840 Specifications: Item: Lens Collar Material: Aluminum Alloy Model: IS TA1840 Color: Black for: for Tamron 18-400mm F3.5-6.3 Di II VC HLD B028 Tripod Mount Ring note: (The other items in the photos not listed here are for illustrating only, not included) Due to the problems of lighting effects and shooting angles, there will be certain tolerances in the product, please understand. The error of manual measurement of the size is within the normal range of 0-2cm.