Plastic bottle funnel

Step 5 Assemble

With the cap on the bottle see how close the pen fits the opening in the cap. If it is too tight slowly whittle a small amount away from the cap opening until you can jam the pen in tightly. If you would like you can apply a sealant inside the funnel and around the pen to ensure there are no leaks and to make more of the liquid flow into the pen and not get trapped in the well formed around it.