PassMark audio loopback cables contain two 3.5mm gold plated stereo plugs which connect the Audio out and microphone in ports of your sound card during sound card loopback testing.
The following are the cable specifications.
Dimensions:
Total length: 330mm ± 0.5mm
Plug length: 14mm ± 0.5mm
Plug diameter: 3.5mm
Conductors:
American wiring gauge: (26(10/0.12)x2F, 0.43mm diameter
Insulation: PBC, 1.0mm diameter
Shielding:
Spiral shield: Bare copper wire, 30/0.10
Sheath:
Material: PVC
Color: Black
Audio loopback cables can be purchased from http://www.passmark.com