What is the relationship between Vallourec and pipe in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

Struggling steel pipe makers including United States Steel Corp, Tenaris SA subsidiary Maverick Tube Corporation, JMC Steel Group Inc's Energex Tube, Russia's TMK IPSCO and France's Vallourec Star filed the case in 2013, saying OCTG imports had been sold cheaply to the United States using government subsidies.

Answer: product_or_material_produced