2020 slot2020 Aluminum Frames Slot Width 6 ; Standard Extrusion Size (mm):. 20 ; Extrusion Type_:: LCF (Economy-Series) ; Number of Slotted Surfaces: Four2020 Aluminum Frames Slot Width 6 ; Standard Extrusion Size (mm):. 20 ; Extrusion Type_:: LCF (Economy-Series) ; Number of Slotted Surfaces: Four