Genuine Daikin 4016517 Indoor Air Filter is the intake screen for a Daikin wall-split, trapping airborne dust and lint as air is drawn into the indoor unit. When it clogs, the unit pushes less air, runs longer to reach temperature, and can let dust carry through to the coil. The genuine filter matches the unit's frame exactly, sealing as designed where an aftermarket cut-to-fit can sit loose.