4 in 1 Filter: All popular receivers, radios, SDRs, and Malachite can be used together. Good products are worth buying. This product contains four sets of band-pass filters. The filters are divided into 4 frequency bands. The P1 filter is 0.5-1.5MHz, which is suitable for medium-wave radio listening. The P2 filter is 4.5-12MHz, which is suitable for short-wave and low-frequency bands. As well as the use of 40-meter amateur frequency bands, the P3 filter is 12-30MHz, which meets the use of shortwave high-frequency bands, as well as the use of 20-meter, 15-meter, and 10-meter amateur frequency bands. The P4 filter is FM broadcast frequency, 88-108MHz. The filter can be used with a one-to-four active splitter to provide pre-filter functions for SDRs, radios, and receivers. Malachite, pre-filter, makes up for the design of the all-metal aluminum shell malachite radio without pre-filter, reducing interference in frequency bands such as medium-wave and short-wave FM broadcasts. The filters are divided into four groups: 0.5-1.5MHz, 4.5-12MHz, 12- 30MHz, 80-110MHz, can be used with a 1/4 splitter to achieve simultaneous reception of multiple channels and frequency bands. Material: Aluminum alloy colour: black Package Contents: 1 x Passive Filter 1 x Machine foot pad Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.