. must be larger then 4 gauge to get a good fit. So they will work down to 4 .
The shrink sleeves are so large that they barely shrink down to the diameter of the fitting which means your wire must be larger then 4 gauge to get a good fit. So they will work down to 4 gauge wire but sleeve size is way overkill on size.
Pros
As advertised. Good product
Cons
The heat shrink may not provide enough insulation in extremely cold environments