You can then dose all of the ground coffee into your portafilter to get an exact and repeatable measurement - a very useful tool in coffee is to be able to repeat your process predictably, which is what this device assists you with. This works perfectly for my home grinder, a Mazzer Mini but should be able to be adapted for almost any other brand of grinder that employs a hopper lock off chute. I chose to use food grade plastic from a juice bottle since the neck of the bottle is rigid (vs say a milk bottle which is thin and flimsy). Also be sure to check that your DIY funnel does not interfere with the grinding mechanism - I was able to ensure that to be true by verifying the spout opening is larger than the grinder input diameter.
Take a look at the video to see how it works. Let me know if it helps you.