Bright-dipped green anodized aluminum bulkhead fittings. 

NOTES:
-The 20-0170 6AN ORB with 8.5mm Barb to 6AN Male Bulkhead Fitting was introduced in Radium Fuel Surge Tanks after 2014. It includes a preassembled Viton O-ring and requires a 6AN ORB (9/16-18 threaded hole) with SAE chamfer to be drilled into the mating part for sealing.
-The 20-0196 10AN ORB with 5/8" Barb to 10AN Male Bulkhead Fitting was introduced in Radium High Volume Fuel Surge Tanks in 2015. It includes a preassembled Viton O-ring and requires a 10AN ORB (7/8-14 threaded hole) with SAE chamfer to be drilled into the mating part for sealing.