Abstract: An improved tubular-type locking cylinder and dedicated key that provides for both theft- and trip-resistant tumbler pin assemblies, wherein the locking cylinder is comprised of an outer housing, a main base, a locking cylinder shaft, and a plurality of tumbler pin assemblies. The improved features are that a detent slot is formed in the interior wall along the locking cylinder shaft recess through the center of the main base body. The locking cylinder shaft consists of a bore through the center of the shaft member up to its top extremity, a movably disposed catch bolt and spring, and a plug obstructing the opening of the bore. A horizontal passage for seating a steel ball is formed in the shaft member at the lower side of a tumbler pin disc. A locating pin is horizontally situated near the upper extremity at one side of the catch bolt. A keyway slot is formed in the shaft member that is contiguous to the upper end of the bore.