The Bubbler Airlock is a simple and cheap airlock that fits demijohns and 5 gallon fermenters.

Easy to use simply remove the red cap fill half full with water, replace the red cap and push into a bored bung, then insert in the demijohn or fermenter.

Be aware that if used in a fermenter, the volume of gas produced may force the water out of the airlock, this will settle down after a few days and the wine etc will be protected by the Co2 produced, simply wait and refill the bubbler.