ROTO LOC THE ULTIMATE UNDER REAMER SYSTEM. CENTER ROCK'S OVERBURDEN DRILLING SYSTEM CASING ADVANCEMENT MADE EASY ROTO LOCĀ® Wings Retracted Wings Extended UNDERREAMER * Sizes from 5 1/2 " to 36 " (140-914 mm) * Wings lock in place to cut full diameter through any rock formation * No expensive starter casing teeth or ring bit left in the hole * Easily retractable wings * Straight holes in pinnacle limestone and karst, eliminating bent or broken casing. * Simple, quick wing replacement.http://www.centerrock.com/