To install this connector in a keystone insert first screw the coupler from the front of the insert into the nut on the back of the insert until the hex on the coupler is pulled into the hex recess on the front of the insert. Pull on the coupler as you screw it in to keep it out of the hex recess as long as you can. Now use a pair of needle nose pliers to turn the nut on the back side of the insert to snug the coupler on the insert. The insert legs will spring open enough to allow the nut to be tightened.
This might seem like someone made a mistake but, given that keystone inserts are a standard size and F-connectors are a standard size, its just a tight fit and there is no other way this can be done. If you look at commercial keystone inserts with F-connectors, you'll probably find that they secure the F-connector by crimping a ring on the connector rather than using a nut.
The connector is typical Monoprice great quality for a terrific price. We Monoprice customers are spoiled! Thanks Monoprice.
The coupler I received was exactly what I needed and served its purpose. The amount of time it took to receive the part was extremely prompt. I will continue to purchase from monoprice.com and recommend others to do the same. You cannot beat their price and service.