Baer Heli Coil Tap - Wire Thread Insert - Bottoming Tap (STI) - Metric - M39 x 4Baer Heli Coil Tap Wire Thread Insert Bottoming Tap (STI) Metric M39 x 4 is the precision tool you reach for when threads break down and need a robust reinforcement. Engineered for durability and accuracy, this tap delivers clean, true threads that accept coil inserts with confidence, restoring strength where it matters most. Why this tap stands out Oversized design for coil inserts: BaerCoil STI taps are manufactured oversized to accommodate the wire