It took me a few tries to find the right size but large seems to be the right fit for my female adult ball python. She is maybe around 4 feet long. I am going to buy a second one for the other side of her enclosure since she seems to prefer this over her other hide.

I bought this for my ball python in size C. I wanted her to have one that would fit her well so she would feel secure. She immediately went in it when I placed it in her cage. She seems to fit perfectly. I think she feels very snug and secure. However, the next day she tried to hide in it, and it lifted. She was curled up and the hide was partially resting on part of her. This hide is lightweight, so it is easy for your snake to lift it. I got her out and held the hide down while she slithered in to make sure she stayed all the way inside. I also noticed that the hole, is a little too small. She can squeeze in, but I wish it was just a tad bit bigger. The hide itself is a great size for her, but it isn't perfect. I am considering buying a size up for her, but I feel that it might be too big. This is a great hide at an affordable price. It just wasn't perfect for me.

Its a piece off plastic but works well for my adult bp. Wish they made a size just slightly smaller though

I have a 4ft ball python male, he gives this two thumbs up. A large would have been too small, he likes to haul his meals in his hide and this affords him the space and privacy to dine to his liking. He's in a 40 gallon breeder tank, depth wise it leaves a few inches on each side, and length it leaves plenty of room for him to do his snake stuff. This is on his hot side and is his favorite hide, if I switch it to the cool side he will just go sit on the cool side and ignore the hide on the hot side. He fits through the entrance just fine, even after eating. It's hard to find hides for the larger snakes that they like but he loves this one. It has held up to the uth and overhead ceramic bulb without warping.

Edit: typhon weighs 2653 grams for size reference. He's a big boy. I have the next size down for my 909 gram male and it fits him just perfectly as well.

I purchased the 9x13" hide box for my daughter's 4 1/2+ foot long corn snake who is rather thick about the middle and was worried that the hide might be too small. My concerns were unfounded- she definitely has room to spare. I considered buying the next size down but after checking out its measurements and comparing it to the hide that Lyra currently has on the warm side of her tank, I'm positive that it would be too small.

Although many claim that corn snakes prefer more cramped quarters, Lyra doesn't- she immediately abandoned her previous hides and took up residence in this one when it arrived. Regardless of whether this hide is used on the warm side or cool side of her enclosure, she can always be found curled up happily inside.

Although the hide takes up a lot of floor space in our 36x18x18 terrarium (see the last photo), it is sturdy enough to set a large water dish on top without it flexing, sagging, or bending. With some well placed fake plants, it also blends into the background fairly well. I also had occasion to contact Pangea in regards to another of their products and their prompt and extremely helpful reply gives us confidence that, if something were to crop up in the future, Pangea would stand behind their product. I would definitely purchase this item again.