Nitrous Distribution Block, 2 In 16 Out - 1/8" NPT Siamese Block, Chrome, polished - NOS Distribution Blocks are precision machined to help distribute balanced amounts of nitrous and fuel to each intake port. All NOS Distribution Blocks use 1/8" NPT “in” and are available with 1/8" NPT or 1/16" NPT “out.” Fittings must be ordered separately.