In this podcast, two NEMA Members describe some basic steps utilities can take to ensure that they are getting quality insulator products.

Suggested Purchase Specification Guidelines for High Voltage Insulators | High Voltage Insulator Toolkit

NEMA published a Standard for guy strain insulators.  The new Standard goes beyond NESC requirements to ensure interchangeability among brands and product integrity over time.

High Voltage Insulator | High Voltage Insulator Toolkit