I have used numerous of the non-shielded plastic monoprice couplers and I would regretfully go as far to say they have about a 30-50% failure rate. These shielded couplers have worked 100% for me however. They are more $$ but I use them for both UTP and STP coupling etc.
We moved into a new house and the existing CAT5e cables weren't long enough to be plugged into an Ethernet switch. Used these inline connectors to extend cables from patch panel to a PoE switch. Both powered (PoE) and non powered equipment worked perfectly.
Ordered these several times over the years and have never seen a failure. Definitely recommend the durable metal construction over plastic if you're planning on burying runs in floors, ceilings, or walls. I haven't tested it, but these should withstand being stepped on or hit by vacuums as well.
PROS: Durable construction. Metal never separates or loosens like the plastic couplers. Gigabit still functions over long, coupled runs, so attenuation is within acceptable parameters
CONS: Need to concentrate when inserting 8P8C connector to make it fit due to snug connection, though this could be counted as a pro as well. Has somewhat larger footprint than most of its plastic counterparts.
Ordered a few of these for a temporary office relocation project. Didn't know where desks were going to end up, and was able to use the couplers to extend prebulit data cables from the switch once desks were in place.
The connections were a little snug, but I didn't have any serious difficulty in inserting the plugs into the couplers. I'd rather they be snug than loose. Couplers are slightly bulky, but not enough to rate an entry in the "con" field above.