The plastic rings on bits?

What is the purpose of the ring around the bits in the picture


In theory, the ring is to act as a depth stop for each endmill. Meaning, in theory, if you installed a bit so the collar was against the collet and you needed to replace the bit (with the same type), you could just install the new one the same way and not worry about the Z height.
They also help identify the bits.


Is there a list of bits in a single location that tells what the bits are best used upon?

Will give you a listing of all the X-Carve bits from Inventables. You can click on each ring color and read the descriptions and what material it’s best used for… You may be inclined to read it and make up a chart… (I might do that down the road sometime…)