Nickel plated spring steel. I measured .760" diameter, .890" tall. Fits most (I can't really think of an exception...) Bigsby tailpieces from the '50s to the present. Looking for a little more height from your Bigsby? This is the spring for you! Nickel plated spring steel. Brand New. Genuine Gretsch 0061715000. UPC 717669211769.