I was definitely able to extend my shaft with this product. Perfection

I wish it had knurling. Then paired with the stubby screwdriver it can make a perfect travel screwdriver.
As it is, the shaft + stubby totals about 35g/17% lighter than the regular 210g vs 175g.
I really like the fact that the shaft to screwdriver magnet is stronger than the shaft to bit magnet. This allows me pulling the bit out while holding the screwdriver instead of needing to hold the shaft.
Knowing Linus it's probably something he considered about when designing.
That isn't to say that the magnet holding the bits is weak, not at all.

It works perfectly with both LTT Screwdriver (black shaft edition) and with my Stubby Screwdriver. Made bit set with all the bit sets and the case I used was just a bit to small for the full size to fit in, but a stubby fit perfectly. Add this extension and now the stubby can be used in the places where the extra length is needed.

Feels solid!

Magnet is great. Easy to remove and replace. Very good for when you need just a little more reach.