I'm sorry folk have been ripped off by a product that doesn't work effectively as I've seen this product in the past. But whilst I thought it's a good idea to black out sensitive ID info instead of messing about with a shredder, I adapted the idea and now keep a broad black marker pen on by my desk just for that job. I sign write and illustrate blackboards for businesses like pubs, restaurants and cafes and so I already use a black marker for correcting errors, tidying up etc. on black backgrounds and for working on top of other paler coloured layers I've already done, smooth surfaces, glass and mirrors. Obviously most folk won't have a large marker just lying about and my 15mm tipped ones cost £2.75 + VAT but vastly cheaper large tipped markers are available, eg for marking bingo cards (dobbers). Save yourself some money and ID theft worry and forget these stamps.