http://blumberger.net/578-2 http://ramblingfisherman.com/2012/01/5-tips-for-centerpinning/ 
FE300 Ferrite Round
- Dia: 77 mm, Height: 23.6 mm
- Output: nom .5 watt and max 1 watt
- Frequency Range: 5000 Fo-HZ
- Net Weight: 65 g
- IMP:8
http://karen-keogh.co.uk/portfolio/the-old-chestnut/ 
FE302 Ferrite Round
- Dia: 92 mm, Height: 29 mm
- Output: nom 1 watt and max 2 watt
- Frequency Range: 5000 Fo-HZ
- Net Weight: 73 g
- IMP:8