#4 External Pipe Nu-Trix Thread Restorer File 8 & 11-1/2 Thread Sizes A Few Easy Passes With The Appropriate Land Of Nu-Trix Over The Damaged Face Of A Bolt Or Pipe Thread Will Restore The Thread Without Reducing The Diameter. As Only The Displaced Metal Is Removed, The Original Fit Is Preserved. Any Bolt Or Pipe Of The Corresponding Thread Number, Regardless Of Diameter, May Be Repaired Instantly With Nu-Trix. For Restoring Bolt Threads, 8 Sizes Of National Fine & National Coarse Threads On Each Of 2 Nu-Trix Bolt Thread Restorers Provide 16 Thread Sizes In All. For External Pipe Threads, A Set Of Three Nu-Trix Pipe Thread Restorers Provide Five Pipe Thread Sizes; A Companion Set Restores The Same Number Of Internal Pipe Thread Sizes. A Set Of Nine Nu-Trix Thread Restorers Is A Valuable Part Of Every Machinist's Or Pipefitter's Kit. Their Small Price Is Quickly Repaid In Time Saved In Repairing Battered Threads. A #9 Metric Nu-Trix Is Now Offered Which Provides Eight Common Metric Pitches. Made In The Usa. Reiff & Nestor Part # 63430