These are a special version of our standard BCP-15's.
Same electrical specs. It's a plate choke optimized for the 45 tube. Standardly airgapped for 40 mils of plate current. It has 50 henries of inductance and 525 (nominal) ohms of winding resistance.
An alternate airgap can be used which yields 40 henries at 50 mils of plate current. This arrangement can be used with 2A3 tube operating at 300 volts on the plate, -45 grid volts, and 50 mils of plate current.
What makes these special is that the plus model depicted in the photo incorporates key elements of our new proprietary inductor designs as highlighted in a post earlier this month.
It has mirror-imaged twin coils in a series-aiding noise cancelling (humbucking) arrangement. It is stacked with premium M3 laminations (.009" thick) which have exceptionally low core losses. Comes in solid brass channel frames. All solder connections are made with a silver bearing alloy.
Available in limited quantities for a limited period of time. These are the best BCP-15's hat I have made.
$250 a pair plus shipping. Email me at firstname.lastname@example.org