Senior Airlock works well for sealing your fermentation vessel. Some brewers prefer to use a Senior Airlock inside bored bungs inside glass carboys or demijohns or barrels. Whether you prefer a Senior Airlock or one piece S-Type Airlock is a matter for personal brewing preference. If you want to read more on S-Type vs Senior Airlocks you might enjoy the following blog on the benefits of each: Senior Airlock v S-Type Airlock

Substitute Airlocks:

• S-Type Bubbler Airlock