The inner upstand pipe shown in the photo is already fitted up to a grow bed, using a thru-tank fitting which has a 19mm thread (supplied).

Two drain holes at the bottom are pre drilled to allow slow draining of the grow bed. The inner upstand pipe is cut to 280mm which will give overflow drainage to a 300mm deep grow bed.

The outer pipe seen in the larger photo (being held above the already fitted inner upstand) is to protect the inner upstand and keep the gravel/grow bed media away from the inner upstand pipe.

The outer pipe is cut to 400mm high to be above the top of the gravel/grow bed media.