Superior Labs 2 1/4" Diamond Mechanical Tachometer SL1010-12009-11-N00. Superior Labs (SLI) is the aircraft tachometer of choice by many OEM’s due to its precision and reliability. The Superior Labs 2 1/4" Diamond Mechanical Tachometer SL1010-12009-11-N00 has a Green ARC of 600-2260, a Yellow ARC of 2260-2385, and a Red Line of 2385. SLI also offers precision aircraft tachometers for aftermarket replacement for most single engine aircraft. SLI manufactures aircraft tachometers for all general aviation aircraft types and offers custom screen printed dials, internal lighting, anti-glare glass, and pre-set engine hours. This specific unit replaces Diamond Katana Models.