One Mag for 8 calibers

[Manonthestreet]

The company advertises the capacity to be:

.223 / 5.56mm: 30
.300 Blackout: 30
.204 Ruger: 30
5.45X39mm: 29
6.8 SPC: 26
7.62X39mm: 25
6.5 Grendel: 24
458 SOCOM: 12
RZE Unimag One AR Mag 5 Different Cartridges - The Firearm Blog

 

[WinterBorn]

Sounds great. But I would worry about reliability. I'm picky about my magazines.