How thick is the Giselle pillowtop topper?

It is 5 cm deep in queen size, measuring 203 cm by 153 cm. That is a modest loft, so expect a softer surface rather than a deep plush layer.

Will it stay in place on the mattress?

Four corner elastic straps anchor it to the mattress. The baffle box construction also keeps the microfibre filling from bunching to one side.

Is it good for hot sleepers?

The microfibre fill is described as breathable, and it lacks the heat retention of memory foam. The polyester cover still holds some warmth, so very hot sleepers may prefer a cotton-covered topper.

Does it help with allergies?

It is described as anti-allergy and dust mite resistant. The cover is polyester and not stated as removable, so it cannot be machine washed like a removable-cover topper.

One queen mattress topper and one storage bag. The bag helps with storing it between uses or when moving.

Can it fix a sagging mattress?

No. It adds softness and a fluffier surface, but it does not add structural support. A sagging mattress needs replacing or a firm support layer underneath.