View inside cannister.
The small hole seen alongside the bolt hole in the centre is the oil inlet hole and is 5mm in diameter. The smaller exit orifice which is 1.5mm in diameter cannot be seen as it is obscured by the edge of the conical, black neoprene seal.
The spokes of the filter rack are clearly seen. The bolt hole is chamfered to allow the centre bolt to easily locate it. The bolt hole contains a steel insert which is not easily seen in the photo. The top edge of the cannister shows machining which creates a good seal on the lid seal.