I purchased a Rain Bird kit to set up drip irrigation and while I'm mostly happy with it, I'm confused about the emitter tubing.

It appears to be a different design than what is in the pictures and instructions. The instructions and pictures included show a simple round hole in the tubing. Whereas, the tubing I received seems to have a long black slit every 1-2 feet. (see photo) It's hard to see in the photo I included, but the slit has a hole that isn't round (therefore the attachments don't fit right) and also has a small piece of plastic across it.

I tried to shove one of the little Rain Bird plugs into one of these slits to stop the water and it only seem to make more water come out around the plug. I tried to shove a little emitter attachment into one of them and while it kindof stays, the water leaks out around it.

What's the deal? Is this a new design that isn't included in the instructions? Are you not supposed to plug those slits? Seems strange, because only some of them are where my plants are, so it seems obvious to me that they should allow them to be plugged. I want to leave some and plug some to save water.