As many as you want!

From manufacturer :

Premium Material - The pool safety cover springs are made of HIGH-GRADE stainless steel, strong and sturdy, corrosion resistant, will work well in a harsh weather.

Universal Fit - Our swimming pool covers pring is a universal replacement part, fits for most kinds of winter safety pool covers on the market.

Strong Elasticity - Measures 7.1 inches, these stainless steel springs has strong elasticity that can secure the swimming pool cover tightly, will not shrink or break