Now I do a fair bit of baking and traybakes are a favourite, so I asked for this for a pressie and for my birthday one appeared. It's really slim, the blade is the perfect width for making 16 squares in an 8" square tin in fact. It's lovely for getting your divided brownies etc. out to serve as well as slicing, the narrowness of the blade mean you can lift just single pieces out at a time without damaging surrounding servings. It's also small enough to leave in the tin for the next piece if you are serving from the pan.
It's made of perspex or something similar with a vaguely sharp edge on all three sides of the 'blade' and will fairly easily cut up brownies and flapjacks without you having to worry about your non-stick pans, on the other hand if you are trying to chip baked on flapjack or the like from round the edge of a tin be CAREFUL, this is not a strong or particularly flexible plastic it has a certain amount of flex and then it will break as other online reviews I've seen have said, I have gripped mine by the blade as low down as possible while releasing my goodies from their tin and it's done a good job but using much force on the handle will leave you holding /just/ a handle! I really like mine and I think, with care, I'll get a good bit of use out of it but I'm not sure OXO made the right choice in materials to make these.