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 retained on polymeric tubing by a flange formed around a polypropylene washer. The washer never comes in contact with the mobile phase.