Copper water pipe: What's the diff between LX and MX ???

Wall thickness. There are types K, L and M in order from thickest wall to thinnest wall. If you have "aggressive" water that corrodes pipes, the L will last longer, if your water isn't a problem, the M is cheaper. Type K isn't normally seen in regular plumbing use. There is definitely a weight difference between types, but you won't readily notice it by hand.

In case no one else answered this, here is a comparison chart. I have no idea what the X designation might be (I've not ever heard it before). Use of type K, L, and M copper is very common terminology.

I'm at the home despot today (here in canada) and I'm wondering how much copper pipe is costing (on a per pound basis) as a multiple of the going market rate for copper (about 4 - 4.5 dollars per pound).

So I'm looking at 12-foot, 1/2 inch copper pipe.

I see some for $24, and some for $13.69. One is labelled "LX", the other as "MX".

They look and weigh about the same.

I figure a 12-foot piece weighs about 2 lbs (maybe 3 tops?) so there's about $8 or $9 worth of "raw" copper in these pipe sections that are retailing for $14 to $24 each.

But what's the difference between this LX and MX marking?

Type K is pretty thick-walled. Type L is a bit thinner and is used for water supply distribution Type M is thinner still and used for condensate drains

X. Y, and Z are Eurpean designations of roughly the same thing. I don't know what combining an "L" and an "X" might mean.