What are those tiers? I can guess yellow belts are tier1, red=T2 and blue T3, but what are the other tiers?
Same question about pipes, there is only 1 pipe, what would tiers be?

<unintentional double post>

The other belt/pipe tiers are only there if defined by other mods. An example for such a mod would be Bob's Logistics mod, wich defines additional tiers for belts and pipes. Tiers are detected by unmodified maximum underground length - shortest is tier 1 (yellow belts in vanilla).

Thanks, I supposed something like that but I rather ask.