Stainless steel tube to ASTM A312, to Schedule 40 (SCH 40). 1/4" and 3/8" are seamless, the other sizes are welded. Suitable for threading to accept the screwed fittings which can be found by Clicking the following link: Stainless Steel Screwed Fittings. Not suitable for potable water until the inside of the tube has been cleaned. Manufactured in the UK by a BS EN ISO 9001:2008 registered company.