what Americans call a "laundry egg," and rather than designate it a good or a bad one, I'd have to call it incomplete, mainly because 30 washes into the promised 300, it needs back-up. Has its merits, but clothes reeking of sweat and mildew still have a whiff of sweat and mildew after they've been through a cycle in my laundry machine. A fainter whiff than before, to be sure, but the whiff is there, gentle reader, the whiff is there.
First, the looks: the thing resembles a cross between a grenade and a washboard, only it's round. Think of a large green frog with a great many warts, throw in one of those rubber porcupine balls that dancers and middle-aged ladies use to work out the kinks in their muscles, and you get the general drift. It's green as the Emerald City and if you bowled it across the floor to a teething toddler (an off-label use that might just work) the kid would enjoy crushing it against his gums. Besides, it rattles, you see, from all those highly-touted ceramic balls in it that are supposed to be ecologically correct. On Amazon.com I find that the warty little thing is supposed to clean laundry without detergents, to ionize (doesn't that sound cool?) the water to repel dirt and stains from fibers with "no residue or chemicals," to be hypoallergenic, antibacterial, and odor-eliminating, to be suitable for all washing machines and water temperatures, and to last for 1,000 loads of laundry or 3 years.
My experience leads me to say that with mildly dirty loads (that day I didn't sweat much) the thing can sort of do its job, but it does it much better when you add laundry detergent. When you've got those stinky mildewy things, the stuff that's been worn at the gym and then spent the night in an airtight smelly sports bag, adding baking soda and vinegar to the detergent helps. I enjoy watching the biowashball do the bump with my clothes as my longsuffering machine whirls them.
Now, I'll concede two things: (1) you can use less detergent than you normally would and (2) those hard little warty bumps probably have a washboard effect--they do your scrubbing for you. But I would not throw them in the machine with delicates and wools. The ball's probably too tough for them. I don't regret buying it: I think, with proper backup, it's a real cleaner. It's just not a miraculous alternative to detergents.
P.S. I do use environmentally proper detergents! Specifially, Frosch.