SFP fiber-optic transceiver (also purchase SFP-GbE upgrade) allows the SFP port on E3Switch Ethernet to DS3/E3 converters to connect to 850nm, 50/125µm MMF up to 500m or 62.5/125µm MMF up to 300m. Finisar model FTLF8519P2BTL or equivalent. Availability: Usually ships the next business day SFPxcvr8519$50.00 Copyright (c) 2011, E3Switch LLC, all rights reserved.