Blue velvet Trinity headphone cable is made with 4 wires of your choice that are sleeved from the amp end up to the splitter in 6mm sleeving which then branches off after the splitter into two wires either side which are sleved in a 4mm sleeving of the same colour up to the headphone ends. See below for wire choices.
 
Main body 6mm
Headphone ends 4mm
Wire type- ofc, occ copper litz, occ silver plated copper litz or pure silver
Headphone type- Any full size double sided entry
Flexibility- 10/10 
Colour- Dark blue
Connector colour- Any