"tube" vs. "tubing"
Solution 1:
From the Wiktionary article on "-ing":
Suffix -ing: Used to form uncountable nouns from various parts of speech denoting materials or systems of objects considered collectively.
Roofing is a material that covers a roof.
Piping is a system of pipes considered collectively.
See the suffix -ing has three actions, according to Wiktionary:
- Forming gerunds - from verbs, obviously
- Forming the nouns to designate something "collectively", as in your examples
- Forming nouns of the action or the procedure of a verb ("the forging of the sword took hours")