Nitrous Distribution Block, 1 In 4 Out - 1/8" NPT Standard Block, Black - 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.