Has anyone used them?

I bought cheap ones from the Christmas Tree Shop one time and they didnt work like Space bags at all.

I see walmart carries a different brand and I am wondering if anyone has used them before? Do they work? I need to start getting all these baby clothes away and have no room. I need a lot of them and they are $$$ for the real thing, but I dont want to waste my money on fake ones that dont work anyway. TIA.