These are both of Furutech's flagship 1/4"/3.5mm adapters. (With a similar design to their flagship carbon fiber connectors.) The CF63-S is 3.5mm to 1/4" and the CF35 is 1/4" to 3.5mm.

If you have a high-end headphone system and use adapters, these can improve the sound to a surprising extent, especially in terms of resolution.

I am the original owner. They appear to still be in flawless condition. (Bear in mind that when you touch them, it can leave fingerprints, which are easily wiped off.)

I would like to sell them as a set. The retail price for each is over $50. My price includes the PayPal fee and insured USPS Priority Mail shipping to the US. (I can ship internationally, but you would be responsible for the shipping cost.)

"Using cutting-edge technology and materials, Furutech's 2-Stage Super Cryogenic and Demagnetizing process significantly improves every facet of audio and video performance. The treatment begins with a deep, conditioning cryogenic freeze of all metal parts, including conductors and connectors. Stage Two exposes the parts to a Ring Demagnetization treatment. These treatments keep all connectors, conductors, and metal parts in a perfect stress-free and stable condition, improving electrical conductivity and so power and signal transfer.

Furutech uses the following conductors treated with the Furutech α (Alpha) 2-Stage Super Cryogenic and Demagnetizing Treatment.

α (Alpha)-OCC
α (Alpha) μ-OFC
α (Alpha) Pure Copper
α (Alpha) Phospher Bronze
α (Alpha) Eutectic Cast Brass"

"Main conductor: RoHS Compliant Rhodium-plated α (Alpha) phosphor bronze and copper alloy
Insulated: POM resin.
Housing Material: Rhodium-plated α (Alpha) copper alloy and Carbon fiber finished"