Now, a down and dirty class list, slowest to fastest!
US Class designation/ARMA class designation - Brief explanation
Junior Prepared - Same class both associations, same mower as IMOW/Super Stock for kids 10 - 15
IF YOUR A HEYMOWER UNDER 16 THIS IS YOUR ONLY CLASS SO DONT REMOVE THE GOVERNORIMOW/Super Stock - This is the governed engine class, great place to start and learn to build,set-up and drive a racing mower. Or for the more experianced racer to just have fun! The great part is you can throw a modified engine on these chassis, if you build them right, and go to the faster classes.
AP/Mini-Sportsman These are the little guys, not the drivers, the mowers. Short,light mowchines with those

off bumble bee engines, Small flatheads 8.5 HP & under! Don't let their size fool you, these little skates are a drivers machine!
SP/Sportsman - The rest of the flathead singles. This is my favorite class, I don't think the racing can get any better! A great step up from the governed classes, light and agile, but the longer chassis makes them alot easier to drive than an APs and Minis and allows for some good tight racing action. The slower speeds and lighter weights allow you to get away with a little bit of rubbin' and bumpin' without necassarily a complete whipe out, but not without a black flag!
CP/Mod-x - OHV Singles and Opposed twins. Now you better bring it boys, this is where things start getting serious! Where engines start getting mad and drivers better be bad, down in the dirt fight it out battle royal of mower madness, man and mowchine gettin' it on! Clean cut mommas boys stay at the house eatin' cookies and drinkin' your milk, but if you got feathers on your tail strap it to a CP/Mod-x and LETS DO THIS!
BP/Super Sportsman - OHV Twins. Can you say hold on to your tailfeathers! Fast is just what these speed demons do for parade laps! Thats not chicken grease in Supermans ears, he lost his hearing breaking the sound barrier at Talladega! Bring your best game, and your biggest wallet. A whole pocketful of Andrew Jacksons will get you in the game, but just barely. Short cut's and budget builds won't put you up front here. If a part can be broken, the Big Twins will do it! Your chasis better be right, your driveline better be right, your tires better be right, and your nerves better be 4140 or your gonna get left! If you don't have a couple of good seasons on a MOWER under your belt don't even try it. Ohh you raced a late model? Good now come learn how to drive! Track champ in a sprint car you say? So strap your tail on a Big Twin and lets take a walk on the wild side....Swindell & Haudenschild? Pfffft rookies!
FX/Pro-x - Single cylinder OHV engines highly modified.This is the AP/Mini gone mad! .Ever drove a Hot Wheel 60 MPH? Barstool racers with a hood. This class allows all the neat go-fast goodies the others don't allow. Centrifugal clutches and RAGBs simulated decks. Highly modified custom chassis,The technicians with fast reflexes class. Another Rookies need not apply class. Where BP's And Super Sportsman are fast, FX and Pro-X are quick, light and agile.
ARMA also has the new Super Mod class. LADIES AND GENTLEMEN, TONIGHTS FEATURE EVENT, THE SOOOOPER M O D I F I E D S!!! WOOOOOO HOOOOO.
If you don't know what they are, you don't need to be racing one so I ain't telling you more than...THEY ARE FRIGGIN' COOL MAN!
Ok, so now some body find my mistakes!