BK7 round cylindrical lenses can be used to focus light but only in one dimension. However, they have the added advantage that they are epoxied into a round cell. The wall thickness is designed to allow full contact with the cylindrical lens when using anSM1RR retaining ring to hold the lens. The application is to use these lenses to focus fluorescence from a gas cell into a thin line imaged onto a photomultiplier tube.