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Window film technology

Selectivity Ratio

Selectivity ratio is the ratio of Visible Light Transmission to Solar Heat Gain Coefficient — the higher the number, the more visibly clear the film stays while still rejecting heat.

Selectivity is the headline metric for "premium" tints. A film with VLT 70% and SHGC 0.35 has a selectivity of 2.0 — high. A budget dyed film with VLT 30% and SHGC 0.60 has selectivity of 0.5 — poor.

High selectivity is what lets Platinum99 stay LTA-legal on the front windscreen (70% VLT) while still rejecting most of the heat. Multi-layer optical films are designed around maximum selectivity.

Selectivity is a useful single number when comparing films across brands, especially for windscreen applications where you cannot lower VLT to gain heat rejection.