A fitting which makes a perpendicular / 90 degree butt joint connector which connects two tubes together. One size only, to suit 50mm tube.
Each fitting has various different sizes (A, B, C, D, E, T). First select which size tube or pipe you want to use, then look at the corresponding size in the table shown below. E.g. You want to use 48.3mm OD tube therefore you need Size D fittings.