Onward to the keyboard! Let's recap this butterfly's metamorphosis so far.

After making its debut in the 2015 Retina MacBook, the butterfly keyboard landed on the MacBook Pro line for the first time in 2016 (pictured at left).

In summer of 2018, Apple launched a repair program, privately blaming dust for jamming the keys—and released updated models with a silicone membrane protecting the key switches (middle image). But problems have persisted.

Lastly, 2019's butterfly switch revision keeps the silicone membrane, but tweaks the materials in the springy metal dome and the plasticky material that covers it.