Lantac UFA-S Ultimate Forward Assist (Solid). - The UFA-S is precision swiss lathe turned & manufactured from certified 4140 Cr-Mo steel giving improvements to strength corrosion resistance and durability over the original materials. - Parts are all heat treated to 48-52 Rc (Rockwell C). - In addition all parts are QPQ (Quench Polish Quench) Nitrided for improved corrosion resistance and enhanced lifespan. - The main Plunger spring is manufactured with the improvement of Stainless 316 music wire (as per ASTM A313) for enhanced corrosion resistance. - Closed end coils are also used rather than the original open ends for improved seating and alignment. Springs are stress relieved and air cooled. - The Plunger Detent Spring is improved and manufactured from Zinc plated music wire (as per ASTM A288) for enhanced corrosion resistance. - Springs are all stress relieved as per the mil specification. - The assembly is retained within the upper receiver with an improved spiral design pin as opposed to a slotted version for increased strength and durability. Pins are fully certified by the manufacturer. - The design of the Cap has been improved by reducing its diameter and snagging potential creating a more streamline surface flow when assembled into the upper receiver. - Exterior surface knurling around the caps edge allows for positive engagement with a gloved or naked hand while removing the circular ridge that exists on the current design. - Weight of the assembly has also been improved to 20.227g (.7135oz) from 22.481g (.7930oz). - All outer details are bead blasted to create a satin reduced reflectivity surface prior to finishing. - Manufactured in the USA from USA sourced materials and finishes.