Do I Need Brass or Stainless Steel Fittings? Before selecting brass for long-term applications, the local compliance rules should be studied. Brass alloys nearly always contain lead (3% by weight would be typical), and while presently permitted in most world markets, their status is under review. In some cases, special notifications might be required. We are seeing labs switching to all steel tubing and fittings. If you have stainless steel tubing, then you should always use stainless steel fittings; and if you have copper tubing then you should use brass fittings. You may want to consider switching to all steel!     Using brass fittings on stainless steel tubing is not recommended. Brass is softer than steel and may not seal onto the tubing as well, risking leaks. You might also see galvanic corrosion, which is a process where the corrosion is accelerated by 2 dissimilar metals contacting one another.