Wear Safety Glasses!
But... This really helps deflect sparks when using a cutoff wheel, but the main reason i made it is for using the wire wheel because they fling little wires all over the place that stick in your clothes and make a mess.
Also helps keep the dust flying up in your face if your using a sanding wheel. Just spin off the accessory thread cap on the end of your dremel and thread this on. Works great on my Dremel and my Milwaukee M12 Rotary Tool.