These spreaders has no variants for each tiers of transport-belts.
However they are enough to be combined with tier 1 or 2 transport-belts.
But they seems bit slower than tier 3 transport-belt (45 items/sec).
Would you like to adjust these spreaders to be suitable for tier 3 transport-belt?

I have not dug into the code to make any modifications besides version compatibility, though I might do that in the future.

As for speed, I have noticed through playing my own games that there seems to be a speed limit in processing by the spreader based on the fastest belt connected. So, if you input on a single yellow belt, you get a single yellow belt's full output. But, if you input on two yellow belts, it uses the same amount of processing, so only half of the input is accepted. I have not used them above red belts, so I am not sure if there are any other constraints on speed at that level.