The tripod mount ring mount on the tripod, it helps you fix and balance your tele lens which is heavy or long lens hanging off the front of camera. 100% fits Tamron and does have same construction.
RING: Advanced CNC processing, High quality Anodized aluminum alloy
RING SPECIFICATIONS:
Color: Black The UNC (Unified National Coarse Thread) is 1/4" and 3/8"
Suitable for: SIGMA APO 70-200mm F 2.8 II EX DG MACRO HSM SIGMA APO 70-200mm f/ 2.8 EX DG OS HSM Item Included: Lens Tripod Mount Ring x 1