If you are particularly tall or have a back problem then a handlebar extension may be a valuable accessory.
Mountain Buggy pushchairs are lightweight and well balanced making them easy to push whether or not the handle is at the ideal height for you - much of the time you are just resting your hands on the handle and maintaining control.
But having the handle at a better height for your can make it more comfortable.
It's probably less to do with your height than the position of your elbows (although the two are of course related) and therefore the angle of your lower arm when holding the handle. The closer to horizontal the more comfortable it feels and the better leverage for manouevering.
The handlebar extension adds about 8cm (3") to the handle height and increases the distance to the rear axle - a tall person generally has a longer stride.
At 6' (1.85m) tall a handlebar extension may be a 'nice to have' accessory , at 6'4" (1.95m) tall a valuable adaption.
Once fitted the handlebar extension can be left on the pushchair, when someone else wants to use the standard height handle simply fold it down out of the way. And of course it doesn't increase the length of the pushchair when folded down for storage or transportation.
Fitting Instructions
The detailed fitting instructions are available online in Acrobat PDF format, it is a large file and may take several minutes to download