HP Module Procurve Gigabit-SX-LC New OEM MINI-GBIC p/n J4858B with 90 days warranty.
It is an extremely fast and reliable SFP (Small Form Pluggable) GBIC. It will work great with your HP ProCurve 4100gl, 5300xl, 2800, 9300m, 2600, or 6108 series switches.
The J4858A will work in virtually all of the same applications as the J4858B.
This industry standard GBIC can be used in switches from companies like Nortel Networks, Cisco Systems, Foundry Networks and others if desired.