Supply stop specs

If I need to buy a compression supply stop to fit over 1/2 copper and connect to a flexible stainless steel supply line for toilets, lavs, kitchen sink, laundry sink, etc. how are the sizes specified?

I did not see a '1/2" compression' stop at the store?!

Are the outlet sizes different for the various fixtures or are they all the same size? What is/are the outlet size(s)?

Sorry if this is a basic question, but I'm trying to avoid too many extra trips to Lowes and the guy in the plumbing section couldn't really help.

Thanks,
Joel

Since 1/2" copper is 5/8" OD, you would be looking for 5/8" compression by 3/8" compression.

Most lav and toilet supplies come with 3/8" ends and 1/2" IP connections for faucets and 7/8" for toilets.

stops

If the guy in the plumbing section cannot help you with this most basic of plumbing questions, maybe he should be selling carpet. Compression fittings are sized by the tubing's outside diameter, which for 1/2" copper is 5/8", and since that is probably the only size stops Lowe's has, your, and the "helper's" choice should have been easy.