VICI Jour offers two types of low-pressure fittings for 1/4-28 flat-bottomed fitting details:

• Flangeless connections utilize several ferrule designs. The ferrule grips the tubing as the fitting is tightened, without significantly reducing the tubing ID.
• Flanged tube end fittings are held onto polymeric tubing by a flange pressed onto the port with a nut and polypropylene washer. The washer protects the flange, yet never comes in contact with the mobile phase.

More information on Properties of Polymers