This is an adapter ring for attaching SWIFT filters to your lens. It is used to attach SWIFT filters to a lens when not using the "Variable ND TRUECOLOR ND VARIO." This is the same product as the one included in the "SWIFT Kit." How to read the size: An adapter with a single number, such as "49mm," allows you to attach a 49mm SWIFT filter to a lens with a 49mm filter thread. An adapter with two numbers, such as "43-49mm," allows you to attach a 49mm SWIFT filter to a lens with a 43mm filter thread. 46mm to 49mm adapter ring for the Swift system. - Brand: NiSi - Model: Adapter Ring for Swift System - Size: 46 mm - 49 mm - Features: Adapter ring for the Swift system Thank you for viewing. ⭐️Click here for other product pages⭐️ ❣️We have items in many genres!❣️ Please come and visit us ♡ ↓↓ #yukimama's shop