The 2SK3537-01MR, 2SK-3537, K3537, 3537 is a 150V 33A TO-220NIS Package N-Channel MOSFET, from FUJI Electric manufacturer is a IC Chips with N CHANNEL SILICON POWER MOSFET. More details for 2SK3537 can be seen below.
The 2SK3549-01MR, 2SK3549, 2SK-3549, K3549, 3549 is a 900V 10A 270W N-Channel Power MOSFET Enhancement Mode Package Type TO-247, Manufactured By Company Fuji Electric Corp.