Basic stuff and I've long wanted finer ones. The coarse one is 4mm then the 2nd one is 1mm, (same mesh as mosquito screen), and the finest is 180 micron so I'm not getting full melt bubble for sure.
I use the first two screens to reduce the size of the pot bits then put small scoops in the last one and shake it just for a half minute or so to get mostly trich heads without too much plant material. I also make oil and mixing the two make some really decent black hash. 1g oil to about 4 or 5g dry sift. About to make a bunch soon with the trim from my last two crops.
When I got them about 27 years ago I didn't even know about dry sift and bubble hash etc. I knew they made hash in Afghanistan and Lebanon by beating pot plants over screens then pressing the powder into bricks. Smoked shitloads of Blond Leb and other pressed hash back in the late 60s, early 70s in Vancouver. I worked in a gas station when I was 15 and these Italian bikers that used to come in for gas were my connection for most things drug related. I'd buy my goods off them then sell them at my junior high school. I was about the only student who rode a 10 speed to school and became to be known as the Peddling Pusher. I kinda made bikes cool and by the end of the school year there was about 50 bikes in the racks every morning. That was 1969/70.