t1 slotTry 2.5 slot and if you get a lot of turbulent noise coming from the GPU fans being too close to the side panel, move to 2.75 slot.Slot opening width : 4mm Finger width : 6mm; Colour : Grey RAL 7030; T1-E = 40mm and 60mm hehts; T1-EF = 80mm and 100mm hehts; T1-EF have an extra cable retainer moulded into