In Level 1, the Extreme Series High Pressure Valved NMR Sample Tubes include an additional standard fluoroelastomer o-ring seal to augment the existing fluoroelastomer o-ring, thus providing a secondary, backup o-ring if the primary one leaks or fails because of wear or physical damage.

Level 3 incorporates additional chemical and solvent resistance over Level 1, Level 2, and the traditional High Pressure Valved NMR Sample tubes, by the substitution of Kalrez® perfluoroelastomer o-ring(s) in place of the standard fluoroelastomer o-rings. 

Level 3 utilizes two Kalrez® perfluoroelastomer o-rings, offering the ultimate level of physical and chemical resistance with the inclusion of a secondary, backup o-ring.