Silica gel can be differentiated based on 
- Form
- Size
- Pore structure or
- Chemical composition

Silica gel forms
granular: Silcarbon SGG
beads: Silcarbon SGR

Silica gel sizes
Silica gel can be produced in various sizes in powder form, granular or spherical.
Standard sizes are 1-3 mm, 2-5 mm, 3-6 mm, 4-8 mm and 5-11 mm

Silica gel pore structure
- A type: fine porous silica gel with an average pore size of
  about 25 nm
- B-type: wide porous silica gel with an average pore size of
  about 65 nm
The pore size distribution has a strong influence on the water adsorption capacity.

Silica gel composition
Standard silica gel decomposes on contact with liquid water. By the incorporation of aluminium oxide in the crystal structure this desintegration is prevented. These aluminosilicates (silica gels with high aluminum content) have a higher resistance to liquid water but a lower water adsorption capacity compared to standard silica gel. Therefore waterproof gels are used there, where in the gas or air phase condensation droplets can occur.  The waterproof silica gel is then applied in filters as protective layer before the standard silica gel.