Will they fit in one of those small dispensers you can put in the leash?

You could probably fold a few or more up and place them in the dispenser but they are not specifically designed for s dispenser

In the item description, this is july 2021, the material says polyethylene plastic. lately i've bought them andthey seem different - are they plastic?

In the product description it says: Features & details Contains 150 compostable pet waste bags with handles, 11.5 inches x 13.5 inches, 0.9 mil A great alternative to regular polyethylene plastic bags BioBags are made from the starches of plants, vegetable oils and fully compostable polymers Great for small to medium dogs of all breeds So I'm not sure if the listing is correct where it says materials...idk who fills that in. Hopefully the manufacturer/company can answer this!

The one with handles, is it the same size as a regular grocery bag? Size in listing confusing

No none are as big as grocery bags as far as I know because they are pet waste. If you want one the size of a grocery bag, you have to get their shopping and produce bags specifically - you can purchase here: https://www.amazon.com/BioBag-RegSHOP-Certified-Compostable-Shopping/dp/B002URKYAC

Is the opening of the bag big enough to scoop cat litter?

Not for me. I have a large cat and a 5.5" wide scoop. It's a tight fit since the bags I received are only 7.4" wide, not 8". Also, any slightly loose litter seems to find itself knocked off the scoop and drifting out of the totally useless hole in the bag (it doesn't secure the bag well when the one side is pulled through the hole on the other side of the bag). I like the concept, but the execution is not as good as it should be. The box itself states they are 8in x 12.6 in, by the way. I'm returning these, and will keep looking for a better solution.