This new smaller format airtight brush washer measures a maximum diameter size of just 3" and a height of just 3-5/8". It holds 310 ml of fluid or about 10 oz which is plenty for most needs. It has two locking clamps for an airtight seal and a removable strainer. This smaller unit is great for when you want to travel light. 

If you need a replacement gasket for the inside of the lid, you can find it here