Please explain fuel cell components

[71DubBugBug]

When looking around
there are metal enclosures, foam, and what looks like rubber bladders

Does one put the bladder inside of the metal enclosure?
Or can the bag and enclosure be used separately?

[clarksongli]

When looking around
there are metal enclosures, foam, and what looks like rubber bladders

Does one put the bladder inside of the metal enclosure?
Or can the bag and enclosure be used separately?

you can get metal enclosures with no bladders, but are not legal for most sanctioned events.

the foam is in there to reduce fuel movement under rapid direction changes

personally i had an aluminum cell, but removed it in favor of one with a bladder. If you are doing just track day events, most places will let you on the track without a bladder as long as it is behind a firewall (don't place it in the passenger compartment).