As suggested I am going to try to explain toy size classifications, first off is that Generation 1 and Generation 2 did not have specific classes with certain exceptions like Whirl and Roadbuster were advertised as Deluxes. Then Beast Wars changed all that and introduced uniform sizing, packaging and price points so we will start here.

Beast Wars – 1996:

• Basic Class: The smallest and cheapest costing $5 USD. sold on blister board packaging (American Dollars) Rattrap was one of these. Sizes vary around 3.5 to 4.5 inches tall in robot mode.

• Deluxe, at  This was one of the strongest performing price points at USD $10. This line was kept for almost all future lines. Cheetor was one of these. Size is around 5 inches tall in robot mode.

• Mega, This class was a disappointment and did not sell well at US$15. Transmetal Megatron was in this group,  Sizes are around 5.5 to 7.5 inches tall in robot mode.

• Ultra: Eight toys at USD$20. Optimus Primal was in this class, Sizes are around 7.6 to 8.5 inches tall in robot mode.

• Super: Optimal Optimus is the only toy in this class at USD$30 and in robot mode stands 12.99 inches tall.

Beast Machines – 1999: added one size class (although Ultra class size was increased keeping the same price):

• Supreme: Supreme Cheetor the only toy in the class at USD$40 and standing 15.3 inches tall.

Armada – 2002: replaced all the names but keeping the sizes except for Basic:

• Mini-Con: Replaced the Basic class, with 3-packs of Mini-Cons standing around 2.3 inches each.
• Super-Con: (replaces Deluxe)
• Max-Con: (replaces Ultra.)
• Giga-Con: A new class at USD$25. Tidal Wave was in this class standing in robot mode around 11 inches.

• Super-Base: (replaces Super, but used the Supreme price point) The only figure of this class was Optimus Prime, who in his Large combined robot mode stands at 11.4 inches.
• “Unicron” was in his own class using the Supreme size standing 15.3 inches in robot mode, at USD$50. 

Universe – 2003: returned to using the Beast Wars classes of Deluxe and Ultra only.

Alternators – 2003: are a class to themselves standing around 5.11 to 9 inches

Energon – 2004: changed the names again:

• Energon Class (replaces Basic)
• Combat Class (replaces Deluxe) 
• Mega Class (replaces Max-Con) 
• Command Class (replaces Giga-Con) 
• Leaders Class (replaces Super Base)
• Omega Supreme was given no size class standing at 14.5 inches tall in robot mode.

Cybertron – 2006: changed some names but kept others:

• Legends of Cybertron: A new class for small bots like Hotshot who stood 3.5 inches

• Scout Class: (replaces Energon Class.)
• Deluxe Class: (replaces Combat Class)
• Voyager Class: (replaces Energon Mega Class).
• Ultra Class: (replaces Command Class)
• Leader Class: (dropped the “s” from Leaders Class)

Classics – 2006: This line dropped down to 4 classes but only one modified name change, leaving the Ultra class out of it.

• Legends: (dropped “of Cybertron”) 

Animated – 2008:  This line jumped up to 5 classes but only one new class.

• Activators: Were legends class size but had a spring loaded simple transformation.

Dark of the Moon – 2011: Made two changes:

• Legion Class: (replaces Legends)
• Commander Class: (replaces Scout)

Prime – 2011: Added two classes

• Weaponizer Class: A bit larger than Voyager
• Maximus Class: Large figures that transform into battle stations for smaller figures

Generations – 2012: These names are now the new classes with the addition of one, all others are gone:

• Legend Class: (returns to replace Legion)
• Deluxe Class
• Voyager Class
• Leader Class
• Titan Class: The largest class ever with:

Metroplex standing tall at 24 inches

Devastator will soon join Metroplex in his class and will be a bit bigger. He will be made up of Six Voyager class figures.

Ok with all that there is some miscellaneous classing to clear up.

Masterpiece Class: Not official but it is used for all Masterpiece (and even third party figures that are intended to be of the line unofficially). This is not a size class because all figures are suppose to be in scale with each other in robot modes at least, since Megatron cannot shrink but to get around this they have included versions of him in gun mode with some figures that is in scale for the other robots to use and he comes with scope, silencer and stock (the latter comes off so it can go back on after insertion into the fist of the figure.) These are much bigger then other lines.

WST Class: Not official again but used in error by many fans calling them “World’s Smallest Transformers”, the actual name is Smallest Transforming Transformers and all of this Takara 2003 line are very small but mostly accurate renditions of G1 figures given the size (the tiny jets even have landing gear.)

Unkown Class: Not official but what some fans like myself use as a catch all for almost anything G1 or G2 or pre-Hasbro.

Seeker Class: Another unofficial class used by some fans for the seven G1 Jets (Starscream, Skywarp, Thundercracker, Ramjet, Dirge, Thrust and Sunstorm *2003 e-Hobby exclusive*) and the two G2 Jets (Starscream and Ramjet) The reason for this class for me is due to them being too large for Deluxe class and too small for Voyager class

Unknown to known class comparisons: Quite a few of G1 and G2 figures can be roughly compared to known classes. G1 Mini-Vehicles such as Bumblebee can be placed in the Legends class, G1 Cars such as Sunstreaker and Sideswipe can be placed in Deluxe but are a bit too small, a bit larger G1 figures like Megatron and Optimus Prime fit in the Voyager class and finally bigger figures such as G1 Metroplex fits in the Leader Class.

well there you go, I hope this clears up sizing and classifications, see you next time.