Is it possible to connect metal tubing (SUS, copper tubing, etc.) to one-touch fittings?

KQ/KQB/KQG one-touch fittings or KF insert fittings cannot be used for metal tubing. The only SMC fittings that can be used for metal tubing are self-align fittings (H/DL/L/LL series) but these are for soft tubing only.