Hi Bunny,
If you are replying to someone’s questions then it’s normally best to reply to them in their topic rather than in a brand new topic.
This is a foundation not a box spring. It’s called the Simple Life foundation that is sold by a number or retailers and has been mentioned many times in the forum (a search on simple life foundation will bring up many other posts that mention it. It and many other relatively low cost foundations are also listed in the foundation reference post here. It would be suitable for many types of mattresses.
Phoenix