SMG/K FA20 T=0.723001 AT003 Feature t=0. 7mm for Supercharged Engine The t=0. 7mm type utilizes a stopper taller than the t=0. 5mm type to provide higher bore seal durability. With a stock pistons, the compression ratio is reduced only by 0. 1; it allows to maintain high heat efficiency. Compression Ratio Stock Thickness: t=0. 6mm (12. 5) HKS Thickness: t=0. 7mm (12. 4) Maintain a high seal with high pressure! Both types are endurable against high engine output.