At fist they do not fit well in T-Locs.
But a sharp knife or rasp will do the little adjustments to fit them in T-Locs, mainly at the front of the inserts.
And it's cheaper then buying new inserts or complete new systainers.
Only Festool does not supply the free credit card stickers on their website, like SYS-STF-D 150 or SYS-STF-Delta 100x150.
They did supply them with the new Classic STF-systainers or with separate inserts.
I made a few T-Loc stickers myself but I am not pleased with the result until now. The text height is not the same as on the original T-Locs. Maybe you can change that with f.i. Acrobat. Does somebody already tried that?
I also post the Classic stickers.