OPTI-GUARD™ sets the standard for extremely low impact, easy to use pre-column protection. Designed for use with analytical (4.6, 3.0 mm i.d.) and narrow-bore (2.1, 1.0 mm i.d.) columns, the patented floating stem design automatically adjusts to any manufacturer's tube stop depth for a zero-dead-volume connection every time. The best part? It's no larger than a standard fitting. Connecting the OPTI-GUARD™ requires no extra tubing, maintaining the minimal impact philosophy that has made the OPTI-GUARD™ line so popular. This product allows you to pick 5 different cartridge packings for test and trial purposes.