I have used these passthrough connectors and they work very well. I use a standard crimper and terminate them as shown in these pictures. The connectors cited have sufficient room to push the sheath of the cable well forward, and when pulled back to get the ends of the wires back into the connector there is still a lot of sheath left for the cable crimping to hold the cable tightly.

Others that I have tried did not work well.

I got these passthrough connectors and I use a standard crimping tool like in these pictures. They worked well. The pictures show cat5e. Using cat6, it's all a little tighter, but still a nice connection.

Later I got some of these staggered passthough connectors, and they did not work well for me since I could not push the cable in as far as needed for a good tight connection. There wasn't any length left after backing the cable out for the sheath to be crimped.

Edit: The wires can be staggered since the connection pieces are different sizes for the upper and lower pins. After all, the contact surfaces all need to be at the same level.