This is a handmade pickup for a double bass. It is not intended for solo use, but rather to be mixed with other pickups to reinforce the contours of a Realist-type pickup. It is designed to be inserted into the wing slot on the high-string side. It comes with a spacer. You can sand down the spacer to fit the pickup snugly, which will provide the best performance according to the design. It is intended to be mixed with a 2-channel head amplifier or preamp. If you don't have those, you can use the Realist pickup for the main sound from the amp, and send the pickup's signal to the sound engineer via DI as a spare channel for sound shaping. Used alone, the sound is flat and hard. The concept is to avoid the "muddy" sound that can occur with body-mounted pickups, while still maintaining a bass-like low end. When trying to get definition in a Realist-type pickup, the sound can become thin and harsh, sometimes requiring a 50Hz 12dB cut, which can be frustrating for bass players. I've been working on a simple solution to address this issue. Please secure it to the tailpiece with zip ties or similar. The purple heat shrink tubing is used to help you avoid mixing up the channels. It's a new item, only tested for functionality, and has a handmade feel.