John Pearse Web Site In 1965, John began developing a guitar string with a longer life and more accurate vibration. His designs were so successful that, over the years, both British Music Strings and Thomastik marketed strings under his name. John Pearse 200L 80/20 Bronze Light Strings (12-53) $5.90 John Pearse 500XL Phosphor Bronze Extra Light Strings (10-47) $6.68 John Pearse 550SL Phosphor Bronze Slightly Light Strings (11-50) $6.68 John Pearse 600L Phosphor Bronze Light Strings (12-53) $6.68 John Pearse 650LM Phosphor Bronze Bluegrass Strings (12-56) $6.68 John Pearse 700M Phosphor Bronze Medium Strings (13-56) $6.68 John Pearse 1400L Phosphor Bronze 12-Strings (10-47/10-27) $9.62 John Pearse Mandolin Strings String Anatomy 101