The above being a hex bolt, eventually need replacing when you've chewed the hex away. Now they're available on t'net at a price, but try getting them from a LBS - !
Tried two on Saturday; Evan's was one of them and the assistants in both shops went scurrying to their spare bits boxes - ! Yep, nothing on the shelf - !
Same with the wee adjuster bolts on vee brakes; the ones that you use to alter the tension on the spring arm to move a brake block away from or nearer to the rim and eventually chew the screwdriver slot on. Had to go to my local ironmonger and buy some 12mm M3 bolts.
Why aren't these two obvious things easily available from LBSs - ?

Same with the wee adjuster bolts on vee brakes; the ones that you use to alter the tension on the spring arm to move a brake block away from or nearer to the rim and eventually chew the screwdriver slot on. Had to go to my local ironmonger and buy some 12mm M3 bolts.
Why aren't these two obvious things easily available from LBSs - ?