How tall is the SMUG playpen, and what size dog fits?

Each panel is about 25 inches tall. That suits puppies and small breeds. Medium or large dogs can clear it or push it over.

How much floor space does a 4-panel set give?

Four panels joined at angles make a small square or corner pen, roughly a few square feet. The 6-panel set adds noticeably more room. Buy two sets if you need a real run.

Can I use it outdoors on grass?

Yes, the plastic is fine on a lawn or patio. On grass or uneven ground the panels are easier to nudge, so stake or weight the corners if your dog leans on them.

Does it need tools to set up?

No. The panels clip together by hand and pull apart the same way. Setup takes a couple of minutes.

Is it safe for a puppy that chews?

The plastic is non-toxic and the corners are rounded, but it is not chew-proof. A persistent chewer can mark or crack the panels, so supervise or choose a metal pen for that dog.