Duotight Push-In Fitting – 8mm (5/16in) Joiner/Coupler The Malt Shop Sale! from 90000 /per Qty. Add to Cart This item is currently on backorder but you can still purchase it now and we'll ship as soon as more become available. Both sides are push-in and compatible with 8mm outer diameter (OD) tubing. SKU:KEG905 8mm coupler duotight equipment fitting joiner Kegging push-in