The Juniper EX-UM-4X4SFP is a 4 x 1/10GBE SFP+ uplink module for the EX4300 family of switches. It can house up to four SFP transceivers, SFP+ transceivers, or a combination of SFP and SFP+ transceivers.
You can also configure these ports as Virtual Chassis ports (VCPs) and use them to connect the switch in a Virtual Chassis or a VCF configuration by using SFP+ transceivers.