Provided is a soaking apparatus to treat materials which require higher accuracy in soaking and improved cleanliness. The outboard section can be a winglet oriented anhedrally relative to a lateral axis of the supersonic aircraft. An IBAD second buffer film is disposed on the first buffer film, the second buffer film having a biaxial crystal texture. the interface end of the spring fingers initially deflectable into an annular groove open to the interface end between the spring fingers and an outer diameter of the spring finger nut. 5 \u03bcm or less, the particle size D90 being a particle size in particle size distribution in which a cumulative volume is 90%. The mechanism can be made of plastic, spring steel or other alternative materials.