OPTIFLEX Secondary Drill Refill for Nodin OPTIFLEX Stainless Steel and Titanium Posts. OPTIFLEX Posts are part of a metal root canal post system and provide optimal retention with the least amount of stress. Swiss Made quality provides maximum retention and longevity. OptiFlex is compatible with other split post systems such as FlexiPost at a substantially lower cost. Save 40%+ compared to FlexiPost brand.