The Hy Power GU4-HF-250 is a 4:1 Guanella HF Current Balun for 160 to 6 meters. It has an SO239 connector for coupling your coax and dual banana jacks for connecting parallel feeders. This is a very efficient balun and maintains a flat SWR curve over the entire HF frequency range when terminated into a 200 ohm matched load. It uses dual ferrite cores and can handle 250 watts continuous and up to 350 watts peaks in a matched condition. These ratings are good up to a 2:1 SWR.
This balun is not waterproof and is not meant to be left in the outside elements uncovered. It can be used outside if placed inside of a waterproof enclosure. If this balun is used on an antenna, such as an antenna used for portable or field day operations, you must provide a means a strain relief. The connections on the balun are not strong enough to handle the mechanical stress from the antenna wires.
The Hy Power GU4-HF-250-M micro Balun has the same "stats" as the regular GU4-HF-250, but is micro in size. It features a BNC rather than an SO-239 jack. The balun enclosure is only 3 x 2 x 1" so it won't take up much room in your backpack on your next QRP DXpedition.