Optolong L2 Dual-Combo Set (L-eXtreme & L-Synergy) for SHO imagesWhat is the L2 Dual Combo Set? L2 Dual Combo Set includes two premium filters: one L eXtreme and one L Synergy. **Already have a 2" L eXtreme? Get just the L Synergy HERE. L eXtreme: The L eXtreme is a dual narrowband filter (7nm) designed to exclusively transmit the key nebula emission lines of OIII (500. 7nm) and H (656. 3nm). L Synergy: The L Synergy is a dual narrowband filter (7nm) that provides high transmission for both the SII (672. 4nm) and