Seems there is a difference in PermaTorque and PermaTorqueMLS
PT is just a laminated steel core
PTMLS is the multi-layered steel
PermaTorque
Fel-Pro PermaTorque® head gaskets include a wire ring combustion seal inserted inside the stainless steel armor. The wire ring design provides highly concentrated sealing around the combustion chamber.
• The rubber / fiber facing material of the gasket is reinforced with KEVLAR® fiber, laminated to a solid steel core to resist torque loss and seal fluids.
PermaTorqueMLS
The latest innovation from the proven leaders in sealing technology ----- Fel-Pro MLS (multi-layered steel) head gaskets are proven to handle big power any way you make it! Boost, nitrous, or naturally aspirated – if you need the ultimate in combustion sealing, you need Fel-Pro PermaTorqueMLS.
• MLS maintains contact pressure between the cylinder head and block
• Seals combustion, oil and coolant despite extreme horizontal and vertical motion between head and block
• Distribute clamping loads strategically across the entire cylinder head for optimized sealing