The invention is concerned with a locking cylinder (1) and a matching key (2), wherein the locking cylinder comprises tumbler pins (6) with a head (7) and a tip. (8). The tip (8) engages in a coding recess (10) of the key (2) and, by withdrawing the key from the locking cylinder, slides along two sliding flanks (2), which follow on one another. The dimensions of the conical surface (9) following on from the rounding of the tip (8) and the sliding flank (12) are made to match one another in such a way that the transitional region (13) between the two sliding flanks is covered by the conical surface in the abutting position.