What guage wires are used ?

RESPONSE FROM MANUFACTURER - CABLE MATTERS: This Retractable Ethernet Cable is made of flat wire and the OD is 1.5*6.0MM. Please feel free to let us know if you have any further questions by contacting us through Amazon's messaging center. Open the product page, click on "Sold by Cable Matters" and then "Ask a Question”. Cable Matters Support Team

Gigabit speed capable and compliant?

Compliant for Cat4/Cat6 and handled Basic Gigabit.

I’d like a compact patch cable like this for IT work. Would this work if it was retracted often?

The retractable portion worked fine and has not failed. The clip to hold the cable into the device is the weak link and on failed within a year of regular use. There are workarounds for repairing the clip using zip ties readily available on YouTube. My only complaint was that the cables are too short.

Are the clear plastic end pieces small enough to insert into a landline phone jack?

RESPONSE FROM MANUFACTURER - CABLE MATTERS: No, this Retractable Ethernet Cable comes with standard RJ45 connectors, and it doesn't fit into a phone jack. Please feel free to let us know if you have any further questions by contacting us through Amazon's messaging center. Open the product page, click on "Sold by Cable Matters" and then "Ask a Question”. Cable Matters Support Team