Both the SERIES 301 and 365 use vitreous silica yarn as the insulation on both the conductors and duplex. This yarn retains its flexibility after exposure to high temperatures. Because this insulation has no binders or impregnations, it may “flower” when stripped.
The vitreous silica yarn’s greater purity performs better at high temperatures than other fibrous glass products. Testing indicates that “contamination” will compromise this material’s upper use temperature. The SERIES 365 construction is a cost-effective, medium insulation build of the popular heavy duty SERIES 301 construction.
For higher temperatures consider SERIES 350.
Watlow: Your Heat Solutions Resource Brochure (EN)
Watlow: Vos Solutions de Chauffage Brochure (FR)