Your search for "EX-UM" revealed the following:

NEW Juniper EX-UM-2QSFP-MR EX4300 Series 2x 40GB QSFP+ Switch Module

SKU: NSN-4692
Condition: New
Shipping: Overnight Options
Warranty: 365 days

Juniper EX4300-48P-AFI 48x 1GB PoE+ RJ45 4x 40GB QSFP+ B-F Airflow Switch

SKU: NSB-0640
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days

Juniper EX4300-UM-BLNK EX4300 Series Blank Switch Module

SKU: NSH-6839
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days