yes they are, they are quite big and waterproof. I used similar ones when my old boys couldn't get to the tray on time or missed.
Trouble is the bag is quite heavy. Do any rescues collect? I only know of CHAT nearish to here, gave them all the food and stuff left over when my boys passed but they wouldn't come to collect
I'm going to ask Cat Protection again. Seems sometimes to depend on who you speak to in the shop
Edit: just got back as walked them around to Cat Protection, 15 mins from me and a different woman took them, said she'd give them to a foster mum. Happy news all round.