Altimeter setting and vnav.

[CAPFlyer]

Windshear of any serious significance at altitude is very, very uncommon, but not unheard of. However, remember that windshear presents in a VERTICAL profile, not a horizontal one with the exception of possibly moving into and out of a jetstream core. Thus, the vast majority of the time you'd encounter windshear is when climbing or descending.

[Caldemeyn]

Thanks again for your help, much appreciated.