The 884-SLR OD3 Attenuator is a stackable OD3 attenuator that can be mounted to an 818-SL series detector to attenuate the input beam. It is the RoHS compliant version of obsolete 883-SL and 884-SL. The clear aperture is 10.3 mm. Note that one attenuator is already included and calibrated in the 818-SL/DB detector. If you already own an 818-SL series detector and want to have the attenuator calibrated together with the detector, you must contact Newport service department.