Features: 1. Tuned port designed for bass drum 2. Extend your low-end frequencies 3. Add More Punches to Your Sound 4. Make the bass part more powerful, and the effect can be adjusted; Simply adjust the tightness of the drum surface 5. The revolutionary amplifier instantly improves the sound of any bass drum. Description: Colors: Black/White/Red (as shown) Material: ABS + Rubber Inner Diameter: 10.6cm / 4.17in Size: Outer Diameter 18.5cm / 7.28", Inner Diameter 10.6cm / 4.17", Height 10.5cm / 4.13" Weight: 190g / 6.7oz Using Method: First, put the protective sticker on the drum skin and cut along the inner diameter circle to make a complete circle. The rubber part of the speaker is stuck on the skin of the drum and the installation is complete Package Included: 1 x Bass Drum Amplifier 1 x Protective Sticker