The MicroOLED Display for Apple's 2nd-Gen Mixed Reality Headset will deliver a Resolution between 3,000 - 4,000ppi
It was rumored in September 2021 that Apple requested FMM sample from AP Systems (APS Holdings) for use with the mixed reality headset. The test must have been successful as AP Systems is building a dedicated plant to produce FMM that will be used in a future version of Apple's MR Headset
Source: patentlyapple.com