This is a simplex SMF OS1 fiber optic attenuator, used in fiber optic links to reduce or attenuate optical power. This fixed value attenuator will reduce optical power by 4dB. It uses male to female LC connection and is used in single-mode (SMF) applications. This attenuator comes as a 2-pack. Our attenuators are cost effective and 100% compliant for all of your networking needs. Our products are guaranteed by federal law to not affect or void OEM warranties.