Focal Polyglass 100 VRS 4-Inch 2-Way Shallow-Mount Component Speaker Kit Reduced mounting depth (1.5 inch) for installation in tight spaces Smooth and precise Aluminum/Magnesium inverted dome tweeter with controlled directivity Polyglass cone made from a layer hollow glass micro-spheres over a cellulose pulp which greatly increases the rigidity of the cone without adding weight Double Neodymium magnet Adjustable tweeter level control