The FC1015 from Cleveland Tank is a brass locking diesel fuel cap with a male thread design, for fuel tank necks that take a male-threaded cap rather than the female style used on most of Cleveland Tank’s other caps. It has a 2.125-inch diameter and 12 threads per inch (12 TPI), and it’s both locking — deterring fuel theft and tampering — and vented, so the tank can equalize pressure properly as fuel is drawn down instead of risking vacuum lock. Brass construction gives it more heft and durability than Cleveland Tank’s standard aluminum caps. At 1.0 lb and 2.125 x 2.125 x 2.0 inches, the FC1015 is a direct-fit replacement for diesel fuel systems specifying a 2.125-inch, male 12 TPI locking vented cap.