This shell fits only the New 3ds XL models. It will not fit any older models or smaller models. 
This a flexible TPU shell to protect your system and add a bit of sparkle. Inside is a frosty white and outside is glitter, making it a bit opaque and perfect for covering up any scratches or imperfections. New in package.
For old 3ds xl model systems, use this product:
https://www.qualityfinds.net/product-page/3ds-xl-glitter-protective-set