Cisco 2-Port SFP GbE WAN Expansion Module for Cisco 4451-X (NIM-2GE-CU-SFP=)
Update 2021) What Are SFP Ports Used For? – Router Switch Blog
Should you use SFP ports in a home / small office network? – MBReviews
Amazon.com: 1.25G Gigabit SFP Copper Ethernet Module, SFP to RJ45, 10/100/1000BASE-T Mini gbic Transceiver for Cisco GLC-T/SFP-GE-T/GLC-TA, Mikrotik SRJ01, Netgear, Supermicro, up to 100m : Electronics
SG-5110 All in One Multi-WAN Security Gateway with 8 Gigabit Ethernet (GbE) Ports。1x SFP, 1x SFP+, Up to 10 Gigabit WAN Ports - FS.com