This is a 2 inch to 63mm adapter. It is commonly used with 2 inch + 63mm rigid pipe and 2 inch + 63mm flexible rigid pipe.
Best to use a plumbing cleaner then pipe cement to assemble. Pipe work pushes inside this part.
*Comes in grey not white as shown in this picture*
Internal Diameter: 64 mm (imperial end) 60 mm (metrice end)
Outer Length: 80 mm
Depth / Diameter: 75 mm