The right piece of gear for the right job.
This S-shaped airlock is perfectly suited for the secondary ferment because it has a smaller chamber, which makes it easier to gauge/see how much CO2 is still coming off the beer. It's also handy when you are cooling beer, as there is less chance of sucking airlock water back into the fermentation.
Since these airlocks can be difficult to clean if they get dirty during the ferment, a 3-Piece Airlock is a better choice to use for the primary ferment.
Please Note: Stopper Not Included.