1/2 L copper has the same outer diameter as 1/2 K or M copper. The same applies to pipe schedules. As a result, a slight increase in pressure losses is realized due to a decrease in flowpath as wall thickness is increased. In other words, 1 foot of 1/2 L copper has slightly less volume than 1 foot of 1/2 M copper.
Definition of omega. 1  1 : the 24th and last letter of the Greek alphabet â see alphabet table. 2  2 : the extreme or final part : end.
c.1400, from Medieval Greek omega, from classical Greek o mega big 'o'  (in contrast to o micron little 'o' ); so called because the vowel was long in ancient Greek. From mega (see mega-). The final letter of the Greek alphabet, hence used figuratively for the last, final of anything (cf. Rev. i:8),