On hydraulic Shimano levers, you can move the levers further or closer to the handlebar. Here’s how to do it, it couldn’t be simpler.
The tools
All you need is a 2.5 mm allen key to adjust the reach of the hydraulic Shimano levers. It adjusts to Shimano 105, Ultegra and Dura-Ace levers. This play is just used to position the lever at the right distance from the handlebar depending on whether you have small or large hands. This setting should not be confused with that of the stroke. The latter corresponds to the speed with which the pads arrive on the disc. This setting is available on the Ultegra and the Dura-Ace of course, but not on the 105…

Pictures © Frédéric Iehl
Time and difficulty
In 2 minutes it should be done! There is no need to disassemble anything to adjust the reach of Shimano hydraulic disc brake levers.
Stage 1

On the outer face of the lever below the axis of the lever, there is the adjustment screw. By tightening it, green arrow, we bring the lever closer. If we can’t do it, it’s because we’re already at the maximum.
Stage 2
By loosening it, orange arrow, it moves away. If we cannot loosen, that is also where we are at the maximum. No need to go further.

Stage 3

The deviations are a few millimeters, less than 1/4 inch.
It doesn’t get any easier than adjusting the reach of Shimano’s hydraulic disc brake levers. In any case, we don’t do several turns of the key, we only do a complete maximum and more often a half ! It is therefore normal for the screw to block at some point, this means that we are at a stop and that we cannot go any further. No need to force, we will damage the cast of the key… For the same reasons, we will make sure that the key is not rounded and that the fingerprint is clean..