Fuel Tank Accessories Locking Diesel Fuel Cap for Freightliner M2 Semi Box Trucks Cap Assembly Aluminum Inside Diameter 2 3/8" Made for Smaller Box/Day Trucks Locking 8.00 Chain & 6.50 Bail with "Diesel Fuel Only" Includes 1 Locking Gas Caps and 1 Set of Keys Sold Individually. Keys will match if bought in pairs.