AivituvinPet Playpen Guinea Pig Cage Small Animal Rabbit Exercise Pen with Waterproof Floor Liner - Extension Playpen ONLY

Q: Is this big enough for 3 guinea pigs?

Definitely enough for 3. We have 4 in it as we speak and they have plenty of room to play and run around. It's a great purchase, durable, easy to move around when/if needed. We added a small corner overhead tent for one of the corners on the open side as another quiet, covered spot for resting and the piggies love it.