Check the listing for details. (2) 3/8" ID (max cable size) FERRITE FILTER - Reusable, Snap-On - stop RFI-EMI. Condition: New. Listed at 9.95 USD. (2) Large Snap-On Ferrite Cores Suppress RFI / EMI 0108 Most purchases qualify for a ** Combined Shipping Discount ** Fast eMail Fast Shipping Guaranteed Good-on-Arrival (2) Snap-On Ferrite Filter Cores Effective, easy-to-use EMI / RFI blocker Fits cables up to 3/8" diameter Price is for (2) pcs I've tested, evaluated and successfully used all our ferrite core sizes. I've eliminated EMI / RFI problems in the HF, VHF and UHF spectrum. Examples: Severe noise on shortwave radios from nearby unfiltered / unshielded electrical and electronic devices, transmitters triggering electronic light switches and false tripping of home alarm system. As incredibly simple and passive as they appear, these things really work! I've even used one of my smaller cores to eliminate the TV interference from my corded electric shaver with a brush type DC motor. Works at either end of the noise path through the wiring. It depends on the nature of the EMI / RFI. Suppression at the source is probably the best approach since it protects all affected equipment in the vicinity. But that is not always possible, such as with a mobile transmitter driving by. Here, the best general approach is to keep external wiring (speaker lead, power cords, etc.) from picking up the interference, and/or keep the interference from passing from the external wiring into the equipment. Every situation is different. There is no one solution, but these are certainly worth a try. If they don't fix you problem, just return them for a full refund. At the SOURCE, attenuates EMI / RFI from transmitters or electrical noise from equipment (computers, motors, fluorescent lights) before it gets into the house wiring through the power cord. Because, once the noise makes it to the house wiring, it can travel through the wiring directly to you radio, TV, computer etc. BUT worse, the wiring can also act as an antenna and 'broadcast' interference to nearby battery operated equipment too. At the RECEIVER, attenuates electrical noise generated by all kinds of AC powered equipment traveling through the house wiring before it gets to your radio, TV, computer, etc. And remember, the wiring can act as an antenna and pickup RF Interference from nearby sources such as mobile radios. So, placement close to the affected radio, TV, etc., may be best in that situation. BI-DIRECTIONAL protection: Our ferrite cores will provide bi-directional protection too. Some equipment is both susceptible to RFI while at the same time, produces it's own RFI. 'Touch Lamps' are a good example. They are strong RFI generators when ON and are susceptible to being turned on or off by strong RF fields. Ferrite cores installed close to the lamp base can solve both problems. INSTALLATION: Installation is simple and quick. Just snap-lock over any coax, audio, AC or DC power cable up to 3/8" dia. Smaller cables can be looped with multiple turns for exponential gains in EMI / RFI attenuation. Impedance (Z) rises proportionally with the square of the turns (T): Zx = T². Attenuate EMI / RFI or electrical noise picked up by long microphone/audio cables. Multiple cores spaced along long lines, can alter (detune) the resonant frequency of cables and more evenly distribute the attenuation for better performance. Generally, placement should be as close to the equipment as possible for maximum attenuation, but as experienced RF technicians know, sometimes, a better location can be determined experimentally. A must for field operations when exposed to unfamiliar outdoor environments and you need to reduce the risk of a nearby mobile CB or HAM transmitter getting into your PA, Music sound system or Video gear. Here's a few common and some not-so-obvious applications: Antenna Transmission Line - Decouple the feed line to the transmitter. Stop the coax from acting as a radiator and detuning your antenna. Mobile transceivers - Use on DC power lines to reduce ignition interference. Fuel Pump - Keep noisy interference out of your expensive car electronics. Telephone - Filter radio signals out of your telephone lines. Reduce RF interference to your TV, VCR, DVD and Stereo electronics. Burglar Alarm - Eliminate false alarms caused by passing 2-Way radios. Block RFI emissions from many kinds of electric / electronic equipment. Examples: Digital Scales, DC Motors, TVs and kitchen appliances. Stop those SPOOKY 'touch lamps' from switching on or off unexpectedly. Cores available for 1/4" cables in other listings. FC.38-2 800 pixels REVISED Rev11/05/20 added sentence to check our store for other listed quantities --> ************************************* ham radio etronic e-tronic hamtronic qba BootsParts USA boots PAYMENT and SHIPPING ** We offer a Combined Shipping Discount for most purchases (e.g. excludes books) if paid with ONE SINGLE PAYMENT with eBay's SHOPPING CART ** Condition of Goods Unless otherwise noted above: NOS (New Old Stock) or better, clean, unused 30 day Non-DOA, Good-on-Arrival Guarantee Untested, but NO JUNK or suspect parts PCB parts are thru-hole, NO SMD/SMT Small parts may be bulk packed Manufacturers and Date Codes may vary Attention International bidders only: Sorry, we ship to US ZIP Codes ONLY. We DO NOT ship Internationally. We ONLY ship to Registered US addresses. We DO NOT accept INTERNATIONAL payments. IMPORTANT: The parts we sell are categorized as new because they are unused, but many of our parts are those rare, hard-to-find, discontinued, manufacturing surplus and / or old stock commonly known in the parts business as 'NOS' (New Old Stock). Some of our stock pictures show date codes which may vary from the actual product shipped. Parts from a larger OEM package may be repacked for smaller lot size orders or for more practical handling and shipping. See our store for other listed quantities. We strive to give full and accurate descriptions to earn your 5-Star Feedback. Any known deficiencies are listed in the detailed description. Datasheets are provided when available. Some datasheets may be close but not a perfect match because of part revisions or because they may be from a different manufacturer. If you have any questions concerning our products please email us before purchasing. Your complete satisfaction is important to us before and after the sale. Thank you. 110520