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For guitars, Siepen has made most use of Gibson and ESP Guitars, with Gibson being his preferred brand nowadays. Up until the late '90s, Siepen mostly used ESP guitars with Blind Guardian co-guitarist André Olbrich, both guitarists making use of custom-made Horizon and Mirage guitars, although Siepen has been seen using other shapes, such as a custom-built model based on the Jackson Randy Rhoads. He can sometimes be seen with a custom ESP Eclipse, but he does not use this model often.