These are 18 inch BNC to BNC jumper cables.  We make them from Amphenol connectors and Belden 8259/RG-58A/U non-contaminating high quality 50 ohm cable.  The connectors are not crimped on, but rather they are soldered on.  Shown in the middle is a specially machined wrench, which we use when assembling the connectors on the cable.  This dramatically increases the reliability because they stand up to more physical abuse and are water tight.    The cables are rated for DC through 5 GHz and are custom made in any quantity desired.  Two foot cables are $28.00 each.  Add or subtract $0.50/ft for cables other than that length.