In the midwest ( worked at a LWS for a dozen years ) the cylls go 20 cf, 40cf customer owned and can trade out at any LWS., (80 cf Q cyll),(150 cf S cyll ) ( 300 cf T cyll.)on Inert gases. (220 cf o2 K cyll )and 20 and 50# co2.
Some Distribs called the 150cf a M cyll and it was a little smaller than an S cyll and was used mostly for Medical 02. Anything over 40cf inert or O2 was a lease or rented tank. That has seemingly changed now. I see people selling tanks from the distribs that only leased before. Airgas and Praxair to name a few.