There are different sizes of waste strainers for different waste holes. You can find detailed diagrams about the size. For example, some of them are at about 80mm internal diametre and 114mm external diametre, denoted as 80/114mm. Please confirm your waste hole size of the existing sink before you buy a waste strainer. These strainers are perfect forgranite kitchen sinksand ceramic kitchen sinks.
In addition, there is also a colander on this page. The colander is suitable for the sink with a sink bowl(exclude the edge) between 405mm and 440mm. It helps a lot for organizing the after-wash dripping dishes and dry them up naturally, instead of wiping them up with a cloth where there may be some bacteria and germs.