I use the same hides. The smallest one works until about 100-150 grams, but the next size up I find is too big. I rotate between reptile basic hides and the exo terra caves. When they start to lift their hides I go to the next size up on the other company product. I find that fills in the gaps where as there is a huge jump between sizes in either company between their own products. (I hope that made sense.. I'm exhausted hahaha)
I'm using the large reptile basic hides for my girls 1500grams-2000grams, but it's too small for my 2200gram spider lady.
I just bought the small & when it arrived, i thought "there is NO way she's going to fit in there"- I have a young snake, who is about 18" and fairly thin.(working on fattening her up now) But she does fit! She can fit all the way in, curled up. But most of the time, she likes to lay with her head peaking out of her hides.