Regarding Aluminium Hydroxide for filler,spec as follow:

Physical properties :
Appearance: White powder 
Molecular formula: Al(OH)3  
Molecular Weight: 78.0                                
CAS No.: 21645-51-2
Bulk Density(g/cm3):Loosed: 1.1
                               Packed: 1.3
Density(g/cm3): 2.42
Shelf life: Longer than 2 years.

chemical properties :
Al(OH)3: 99.6% min.
Al2O3: 65.1% min.
SiO2: 0.03% max.
Fe2O3: 0.02% max.
Na2O: 0.2% max.
L.O.I.: 35% max.
Moisture: 0.1% max.
PH: 7.5~10
Whiteness:93% min.
Particle Size:D50: 75~95um
Packing: in 25 kgs bags.

We have different size,fine, ultra fine, and also coated by Silane or Stearic Acid.
Particle size D50: 75~90um,50um,25um,20um,14um,10um,5um,3um,1um.