Someone was asking about 316L. I came across this looking for other things

What does the L mean?

L-grades have 0.03% carbon maximum. L-grades are resistant to sensitization in short-term exposures or heat treatments. L-grade often have slightly lower (typically 5,000 psi less) minimum strengths than standard stainless steels.

Most standard grades of stainless steel have 0.08% maximum carbon and are suitable for use in non-welded parts and equipment; in case of welded applications these parts are used for light-gauge applications
Source is

http://www.lenntech.com/stainless-steel-316l.htm