Boundary Layer Capsule BLM 03 C
The small dimensions of the BLM 03 CG and its matte gray surface allow for a particular unobtrusive placement. It can often be disguised or hidden, e.g. under a light tablecloth.
Any boundary-layer microphone must be placed on a sound-reflecting surface large enough for adequate low frequency pickup. A table top may suffice for speech applications such as conference recording, but most setups for music recording will require a larger surface.
User Guide

BLM 03 Cg mounted to the lid of a grand piano
The BLM 03 C can also be placed in a grand piano, with the lid either open or closed.
Colette
CCM