Cavalry VBU - what does it signify?

Hi,

Looking over a number of Hellenistic periods, and there's a wide range of cavalry across armies in the VB 3-5 range. I was just wondering if there was a consistent pattern to what the different VBU values signify?

For example, in the Indo-Greek list, Indian cavalry can be taken as CL with a VBU of 3 and Javelins, or VBU 4 without. Is this a transition from light skirmishing cav to lancers? There's a wide range of greek cavalry that comes with a base VBU of 4, but which can be upgraded to VBU 5 - what does this upgrade signify?

FMB

You have to consider the I value as well. So a 3-1 CL with javelins might upgrade to 4-2 "battle cav" and lose the javelins.

Generally CL are 3-4
MC 4-5 and HC 5-6. Knights and Cataphracts 7+. I think these are generic ranges rather than indicating a certain piece of equipment or weapon.