Please don't waste your time or money. Although very sharp they're extremely brittle. We have had ceramic knives for the kitchen and they're so sharp you don't realize you've cut yourself till the blood shows up however they chip and break so easy.
My daughter broke the last one we had not long ago just by banging the edge on our counter top, not hard at all but that's all it took and there went $30. Could you imagine just running into a piece if gravel what it would do?