impingement cooling insert 5 by means of a plurality of rib form or circular spacing elements 21 forming an interspace 22 the cooling medium passage 23 enclosed inside the impingement cooling insert 5 is flow washable by a cooling medium the impingement cooling inserts 5 additionally have impingement cooling holes 25 through which flows cooling medium flowing in the cooling medium passage 23 and can subsequently impinge perpendicularly upon the surfaces 19 of the side walls 11 13 in order to cool these the impingement cooling insert 27 viewed in the direction of the blade axis 2 a is formed consequently from two separate parts 29 31 which by a section 30 32 in each case overlap each other in an overlap area 33 35 the overlap area 33 35 lies as a consequence outside the mean blade airfoil height the bottom part 31 of the impingement cooling insert shown in fig1 is fixed in the connecting area gastight on the lower platform and the top part 29 is fixed gastight on an upper platform which is not shown for the avoidance of leakages as the hot blade airfoil 2 b expands more in the direction of the blade axis 2 a than the cool impingement cooling insert 27 during the operation of the gas turbine a movability.