The Harmonic Stabilizer is another exciting innovation from Mathews, Inc.
The Harmonic Stabilizer is purposely tuned to be out of phase with Mathews bow models that have longer risers, and can dampen more than 75% of residual vibration.
When placed in the bottom Harmonic Damper hole the Harmonic Stabilizer will give optimum performance. Another Harmonic Stabilizer can be purchased and put in the top damper hole for added weight but little is gained in post residual vibration.
One Harmonic Stabilizer will be standard issue on the majority of newer model bows and can be purchased as an accessory to retrofit most Mathews bows currently equipped with Harmonic Dampers.

This is the older model, but still current and the correct item for the Mathews Tactic bow.
Most newer models like the TRX's have the taller conical shaped EHS Harmonic Stabilizers, but these ones will also fit.
See pictures for comparison.
These are NOT suitable for the newer hunting model bows (V3, V3X and Prima, they need the smaller Nano 740 damper) 
Text on harmonic part is red or black matching the rubber bits, not yellow as pictured