Bright-dipped green anodized aluminum bulkhead fittings. 

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