With the Lindy USB Type C/ Thunderbolt 3 Port Blocker, you can quickly block open ports and easily prevent users from connecting cables, devices or inserting foreign objects without permission. The USB Port Blocker is made up of a combined 'key' and 'lock' assembly which plugs into the USB port. To use, simply plug the 'key lock' into the port and release the latch - the lock remains in place Plug the key back into the lock to remove. Easy With this neat little device, system administrators can physically prevent users from connecting Pen Drives, Mobile Phones and other USB Mass Storage Devices to their computers to copy data and introduce viruses. Package Contents USB Type C Port Blockers (Without Key) - Pack of 10, Green.