They write well ink flow is good without globs of leaking. They function well as markers.
They are really hard to clean off. Water won't help it budge. Glass cleaner and firm pressure with a Kirkland papertowel didn't even get it all off. I let it soak with glass cleaner and scrubbed 3 times to finally get it off - it was only on the meal planner 1 day to test it.
In the end - no I would not recommend because they are too permanent. Maybe if you're a business and doing an outside sign that needs extra durability - but I don't want to scrub so hard just to update our menu.
Updated to 5 stars!! The 2mm markers useless to me as stated above.
The 1mm worked out okay. I had to go over some words twice... but overall they are working out. I love the colors.