The main feature two channels in the uptube
Exhale went up one channel and inhale came in the other.
Co2 is heavier , so when you exhale in a regular snorkel there is still an amount of co2 exhale in the uptube and the next inhale is partially exhale and not 100 % fresh air.
The 2 channel uptube guarantees every inhale is pure fresh air .
Simple but effective /-).
Very interesting.. Honestly, you should ask admin to remove your post so no one else gets the idea.
It does sound a bit better than the one I used back then ;)