Extended AE Crystal Assembler, Fixer and Circuit Slicer
This guide covers the three benches Extended AE adds on 1.21.1 and why the 1.20.1 build looks almost empty beside it.
Three benches, all new on the newer build
Crystal Assembler — 39 recipes
Circuit Slicer — 9 recipes
Crystal Fixer — 6 recipes
None of the three exist on 1.20.1. Together they carry 54 recipes, which is more than the mod's entire crafting list on either version.
The Crystal Assembler at 39 recipes is the centrepiece. The Crystal Fixer at 6 is its counterpart — a repair or restoration path for crystals rather than a production one, which is the kind of quality-of-life the addon exists to provide.
What 1.20.1 has instead
One category: Circuit Cutter, 4 recipes, filed under a different namespace entirely. The bench does the same job the Circuit Slicer does on 1.21.1, but with fewer than half the recipes and under the mod's older identifier.
That namespace change is the practical trap. If a recipe lookup for the circuit bench returns nothing, you are almost certainly searching the other version's name.
It reaches into two other mods
On 1.21.1 the recipe list includes an 
Inscriber entry with 3 recipes and a Transform entry with 2, both belonging to Applied Energistics, plus single Crushing and Enriching recipes from Mekanism.
Those are small numbers, but they show the addon integrating outward rather than only extending AE2 inward. None of them appear on 1.20.1.
Crafting is the only category that shrank
50 recipes on 1.21.1 against 55 on 1.20.1. Everywhere else the newer build gained; here it lost five, which is roughly the volume that moved to the new benches.
Scale
79 pages across 44 items and 35 blocks and no structures — an addon, not a standalone mod. Without Applied Energistics installed there is very little here to use.
Which version to run
If the pack is on 1.21.1 you get the Crystal Assembler, the Fixer and a circuit bench with more than double the recipes. On 1.20.1 the addon is essentially four circuit recipes and a crafting list. For this mod the version gap is not a detail — it is most of the content.