A set of 48 filters are included in WFPC2 with the following features: . ... In addition to the above complement of broad and narrow-band filters, WFPC2 features a set of three specialized quadrant (quad or Q) filters in which each quadrant corresponds to a facet of the pyramid, and therefore to a distinct camera relay. ... With the exception of the quad polarizer and blocking (Type "B") filters, all filters are designed to be used alone. ... Redshifted [OII] and CH4 narrow bandpass quad filters. ...