ACM (Aluminium Composite Material) cladding consists of two thin aluminium skins bonded to a core material. The controversy surrounds ACM panels with a polyethylene (PE) core, which is combustible and was found to have contributed to the rapid spread of fire at Grenfell Tower. ACM with a PE or mixed core has been removed from many buildings in the UK and is banned from residential buildings over 18 metres. ACM with a FR (fire-resistant) mineral core is considered compliant for many applications.