This balun is a 49:1 balun for an end-fed antenna. It only needs to be matched with a 20m long oscillator (remember it's standard 20m) to resonate naturally in the 7, 14, 21, and 28 MHz amateur bands. Height changes have very little effect on the resonance point, making it ideal for HAMs with some practical skills (build the 20m oscillator yourself). The magnetic ring is a custom-ordered magnetic ring. The M is also custom-ordered for extension (the short M-mounted M male head is screwed on or off). The magnetic ring uses PCB fixing for long-lasting stable and reliable operation. Key Parameters: 5-35MHz VSWR < 1.5 Insertion Loss < 1.5dB Power Handling: 100W PEP (SSB) (The balun is safe after a 30-minute continuous emission test; parameters are the actual standard, we will never overstate to 150W). Color: As Shown Material: ABS Package Contents: 1 x End-Fed Antenna 49:1 Balun Note: Light reflection and different displays may cause the color of the item in the picture to differ slightly from the real thing. The allowable measurement error is +/- 1-3 cm.