From a post to Baen's Bar BuShips dated October 21, 2002:

Administrative and tactical organization of the RMN

DesDiv = Destroyer Division
DesRon = Destroyer Squadron
DesFlot = Destroyer Flotilla
CruDiv = Cruiser Division
CruRon = Cruiser Squadron (could be light or heavy cruisers in most navies)
CruFlot = Cruiser Flotilla (a formation which applies only to light cruisers, which are sometimes organized into flotillas rather than squadrons, although this is not RMN practice)
BatCruDiv = Battlecruiser Division
BatCruRon = Battlecruiser Squadron
BatDiv = Battle Division (may be BB, DN, or SD)
BatRon = Battle Squadron (may be BB, DN, or SD)
CLACDiv = LAC Carrier Division
CLACRon = LAC Carrier Squadron
LACRon = Light Attack Craft Squadron

    At the moment, the number of ships assigned to most of these units is subject to change as the RMN tried to decide which of the Janacek changes to retain and which to get rid of. As of War of Honor:

DesDiv = 3 to 4 DDs
DesRon = 3 to 4 DesDivs (9 to 16 DD)
DesFlot = 2 to 3 DesRons (up to 32 DDs, usually with an attached CL flagship)
CruDiv = 3 CA or 4 CL
CruRon = 4 CruDivs (12 CA or 16 CL)
BatCruDiv = 3 BC (was 4 BC pre-Janacek)
BatCruRon = 2 BatCruDiv (was 3 pre-Janacek)
BatDiv = 2 BB, DN, or SD (or combination thereof)
BatRon = 3 Bat Div (was 4 BatDiv pre-Janacek)
CLACRon = 3 CLACDiv (was 4 pre-Janacek)

    As you can see, the lighter ships' unit organization tends to be much more flexible. It should be noted, as well, that squadrons in the RMN are permanent administrative units, not necessarily tactical units (although there is a distinct tendency for cruisers and above to be kept together as much as possible as tactical units, as well). Thus DesRon 21 might consist of 16 DDs operating in 4 separate forces of a 4-ship DesDiv each and deployed light-years apart on an as-needed basis. The fact that light units routinely need to be detached as escorts, scouts, couriers, etc., helps to explain why their unit organization is so much more flexible than for larger units, which are not so likely to be detached.

    Cruisers, of course, fall into a special category as the medium combatant maid-of-all tasks. Cruisers very seldom operate as complete squadrons unless assigned to a task force or fleet organization, and even there, the TF or fleet CO has a distinct tendency to keep peeling off invidual CAs or divisions of CLs for all sorts of jobs.