When buying new headphones, you choose between on-ear or over-ear before you make a purchase. Once you do, that’s your option. There are few companies that offer the ability to change between the two styles, but that functionality is far from the norm.
With the MW50+, it lets you change the earpads on its MW50 wireless on-ear headphones to make them an over-ear set in a matter of seconds. The earpads on all of Master & Dynamics headphones, both wired and wireless, can be removed, so including a second pad to change the wearing style makes a lot of sense.
Read more about this here: https://www.engadget.com/2018/05/15/master-and-dynamic-mw50-plus-headphones-hands-on/