Great value for money. My Mother-in-law has one and we have just used the 2nd one. Nice and solid - does what it says on the tin. I'm sure you could buy better quality but for what be want they are plenty good enough.
These are not rubber as stated in the description - they are hard plastic and pretty cheap and nasty really. They have teeth like grips on the underside of it presumably to hold it in place better on the floor. I'm pretty sure this would scratch a wooden floor. I have already returned them.