Porter SENTRY-34AV Sentry Sedate Portable Enclosed 4 Cylinder O2/N2O System AVS Dual Locking Doors Holds 2 O2 and 2 N2O E Cylinders (NOT Included) A side hook conveniently holds the breathing circuit and hoses Sturdy cabinet design features both internal and external storage The dual locks ensure safe, secure cylinder storage Large locking wheels allow.