BMW 4 Series models sold from 2014 to 2020 and Z4 models sold from 2009 to 2017 have ‘hard-top’ roofs made from metal and plastic instead of the soft, fabric top used in most convertibles.
Hard-top convertibles were popular in the early 2000s because – with the roof up – they give you about the same level of quiet, warmth and security as you’d find in a saloon. That’s great, because thanks to the British weather most convertibles are driven roof-up most of the time. However, hard-top roofs are very heavy, which reduces fuel economy, and very bulky when folded away, which reduces boot space.
The design of fabric roofs has improved to the point that a hard top no longer has any real comfort advantage, so BMW switched to soft tops for the latest 4 Series and Z4.