I quite like them 3M cable jointing kits,have used them more times than I care to remember.
They give a really good seal, provided you follow the instructions.
After you have done a few, they are just like learning to ride a bike, really, its simple!.
I remember using 4 of these kits all on the same job, and on the same Neutral-Screened cable, too!.
Excavator Operators, Eh?.