4.5" pockets are considered tight. Anything smaller would be considered real tight. 5" pockets used to be standard, but now about 4.75 in the back of the pocket is normal. There is no absolute "standard" now that I know of. Just take two balls and slide them to the back of the pocket on various brands of tables and you will notice slight differences. If two balls will barely drop into the pocket at teh same time that seems to be normal now. If they jam they are shimmed tight.