Designing with ferrite binocular cores can be frustrating as there are different formats in which data is provided, and data for different mixes on the same dimensioned cores appear inconsistent.
There are several source of the Al parameter for some common cores, often from resellers rather than manufacturers.
BN61-202 (Fair-rite 2861000202)
- Fair-rite: 320 (0%)
- Toroids.info: 475 (+48%)
- Amidon: 380 (+19%)
BN61-302 (Fair-rite 2861000302)
- Fair-rite: 230 (0%)
- Toroids.info: 277 (+20%)
- Amidon: 300 (+30%)
BN61-2402 (Fair-rite 2861002402)
- Fair-rite: 160 (0%)
- Toroids.info: 250 (+56%)
- ThePartsPlace: 250 (+56%)
There is large unexplained differences between various source for Al specifications for a core that is quite probably from Fair-rite in all cases.
Be wary of where you source data.