Augustine produces 4 different series' of classical guitar strings The well known sets (CLASSIC: black, red and blue) have identical treble strings in normal tension, the 3 sets differ Sin the tension of the sound bass strings (black = light/normal, red = medium, blue = high). This logic continues in the following series': All GOLD strings have gold-coloured brass wound bass strings and are always in light/normal tension The IMPERIAL series has precision round treble strings in high tension. All Imperial sets have the famous bass strings from the well-known sets and differ in the different tensions (black = light/normal, red = medium, blue = high) The REGAL series has precision round treble strings in extra high tension. All REGAL sets have the well-known bass strings from the famous sets and differ in their different tensions (black = light/normal, red = medium, blue = high) The Paragon Carbon sets are new, with their clear fluorocarbon treble strings in combination with the legendary Classic bass strings in medium and high tension. Classic Red Label medium tension Standard treble strings in Regular tension Silver-plated bass strings in Medium tension Diameter and tension: E1: .028”/0.71mm, 7.81kg/17.21lbs H/B2: .032”/0.81mm, 5.84kg/12.88lbs G3: .040”/1.01mm, 5.56kg/12.25lbs D4: .0295”/0.75mm, 7.2kg/15.89lbs A5: .035”/0.89mm, 6.9kg/15.27lbs E6: 0425”/1.13mm, 6.68kg/14.72lbs Set Red medium Made in United States