Apple‘s new Vision Pro mixed reality headset packs advanced technology into a small form factor, but some reviewers are saying the device feels too heavy for extended wear. Apple executives contend they couldn’t make the Vision Pro any lighter given its components.

In interviews with Vanity Fair published Thursday, Apple’s VP of industrial design Richard Howarth said “there’s nothing we could have done to make it lighter or smaller.” The Vision Pro incorporates magnesium, carbon fiber and aluminum. Meanwhile, VP Mike Rockwell of Apple’s Vision Products Group stated that Apple “packed just about as much technology as you could possibly pack into that small of a form factor.”

Apple CEO Tim Cook recalled to Vanity Fair that early prototypes of the headset were much bulkier, saying past versions were a “monster” in size and “weren’t really wearable by any means of the imagination.” The final consumer Vision Pro model weighs between 21.2 and 22.9 ounces depending on configuration.

Reviewers have frequently cited the Vision Pro’s weight as an issue during prolonged use. Mark Spoonauer of Tom’s Guide felt the headset “weighing on my cheeks” after 30 minutes. Joanna Stern of The Wall Street Journal described the sensation as a “face crush.”

Stern and other reviewers praise the technological innovations in the Vision Pro but say the weight could still be a barrier for some consumers. Apple executives made clear engineering tradeoffs were required to achieve the target size and capability. With future models likely on the horizon, reducing weight while maintaining performance will be an area of focus.