The Beta 91 is a boundary mic intended for use inside a kick drum. It uses the mic capsules from the Beta 98; the RPM108 cardioid capsule provides a half-cardioid response in the Beta 91. Presumably the RPM110 provides a half-supercardioid response.
The photos shown are representative of the units we have for sale and are not necessarily of the exact unit you'll receive.
These sell new for between $240 and $300.