water lines

I know one should replace rubber water hoses with metal. I did that to the connections to my toilets and on the washing machine. In the photo you can see the black water lines under my sink that go from the shut off valves up to the faucets in my kitchen. I tapped them and they are not rubber but instead seem to be a hard plastic. Is this normal and good?

I went to Home Depot today. They opened a box with a Delta faucet and it had water lines that looked just like mine. The water lines are integrated. Their website says it is Pex. The description has -"DIAMOND™ Seal Technology is the revolutionary water delivery system that combines a durable DIAMOND™ Valve with InnoFlex® PEX waterways."

Read more: http://www.deltafaucet.com/smart-solutions/diamond-seal-technology.html#ixzz2zqG98Mjl

They are normal. I have always had good luck with them as long as they are not cut shorter.

We have been seeing more and more plastic because only then the manufacturer does not have to prove that it is truly lead-free.

Lead-Free is the new thing in plumbing.
Lead free solder was done in the 80's, and now they're going after faucets. You will be seeing more and more plastics.