Well I'll add my 2¢. For a Joye 510 they don't work at all. They are just too big in diameter. Tried on 3 and I just didn't feel like trying to force them/shave them down. They do fit the imitation DSE 510's, 901's and RN4075's (which they resemble). That some will feel they work better is understandable as the stock filler seems nicer, is less densely packed and tops off nicely. Better than most factory carts.
The basic design seemed nice when I first saw them, but the main problem is the length of the liquid cup. It's had to tell from the pics but it could have been considerably longer for more capacity. There's about 10mm of wasted space in the mouthpiece. Extending the liquid cup to allow about 3mm of space (should be enough for the draw) would have increased capacity by about 30%.
Checking capacity, which they claimed was more, yielded disappointing results.
Using the 'drops' method (not the most accurate) I filled these carts (empty, no filler) from the same bottle to the very brim.
- H20 = 19
- RN4075 = 15 (fits Joye tight)
- DSE 510 = 16
- Joye 510 = 18
- DSE 901 - 21 (fits Joye tight)
They work well on the RN4075 (a great DSE 901 substitute) so they won't go to waste.
For folks into SLB/DSE 510's these would be a nice upgrade form the stock carts.
Almost a cart mod and a bit more capacity.
That said H2O's shipping was very prompt.