The 490T and 498T are both pickups for electric guitars made by Seymour Duncan.
The 490T is a humbucking pickup designed to emulate the tone of a Gibson Les Paul, while the 498T is a hot-rodded version of the 490T with more output and emphasis on the upper midrange.
The 490T has Alnico II magnets and a vintage output while the 498T has Alnico V magnets and a higher output, which gives it more sustain and clarity.
Both pickups are great options for guitarists looking to achieve a classic, vintage tone, but the 498T may be a better choice for those who want more output and definition in their sound.
