Dynaudio model Stand 6 filler quantity?

Looking for some insight from anyone here who may own a pair of Dynaudio Stand 6 speaker stands. I recently purchased a used pair, and before their arrival wanted to get ready some material to fill them with. For purposes of this question let’s assume it will be kiln dried sand. I’ve searched everywhere but can’t seem to find any info on how much sand (in lbs.) each stand can hold. Not certain I would fill them completely, but “full” is a good reference point from which to start. 
Anyone?  Guesses welcome. Thanks in advance.