These are bulkheads with panel mountings of 5/16-24 UNF threads, 1/8” and 1/4″ NPS threads and a mounting flange. The first barb size is outside the panel, the second on the inside. Available in Black Nylon, Natural Nylon, Polypropylene and PVDF. Barb sizes are 1/16”, 3/32”, 1/8”, 5/32”, 3/16” and 1/4″. (order as BN, NN, PP, PVDF)