Radiofrequency ablation (RFA) of veins >12 mm in diameter has been a controversial subject since the first-generation device was submitted for Food and Drug Administration (FDA) approval. Veins >12 mm were excluded in the initial study. Many insurance carriers used >12 mm size as reason to not approve the procedure. As the concept of tumescent anesthesia was better communicated, RFA was used for large veins. The 12-mm size limit was not used in the studies for the newer ClosureFAST catheter approval, yet remains in force with some insurance companies. Our objective was to determine whether vein diameter >12 mm had effect on closure rates with the Closure-FAST catheter.