To make the jar leak proof, you need to use both silicone seals correctly. The flat seal goes between the filter and the glass jar, and the seal with a raised ridge goes inside the lid before you screw it on. The bump goes up, toward the top of the lid.
To make cold brew coffee, start with ratio of 1 part coarsely ground coffee to 4 or 5 parts water. Let it sit on your counter or in your fridge for 24 hours. This makes a strong brew, so you will probably want to dilute it. Serve it hot or over ice, add sugar or dairy, or any other way you like!
For a pint jar, use 1/3 - 1/2 cup coffee.
For a quart jar, use 3/4 - 1 cup coffee.
For a half gallon jar, use 1 1/2 - 2 cups coffee.
To make a more concentrated version, just use more coffee grounds and / or steep for longer. Cold brew coffee is commonly made very strong and diluted at serving time.
A higher quality coffee grinder will give you a more consistent coarse grind. Cheaper grinders produce a mix of coarse all the way down to powdery grinds. This filter is very fine, but silty coffee grounds can get through.
You can also use this filter to make hot coffee. Just put the grounds in the filter, pour in 200 degree water, and wait a few minutes.
If your filter is already in use, you can put your coffee grounds or tea directly into the jar. Once your filter is available, pour the contents through the filter into a new jar.
They are 10cm, 15cm, and 21cm tall. The mesh part is 7cm in diameter.
Dishwasher safe, and I find this the easiest way to clean it.