The BH coils will fit the F4 but not the F5. I have the 4and 10 inch BH coils I bought these coils for a Discovery 2200, 8 years ago I have used them on 2 discovery 3300's and now I use them on my F4.They are both great coils .I have used the DD stock coil for my F4,but prefer the 10 inch BH because of greater depth and easy precise pinpointing. The 4 inch in my estimation is the best for trashy areas and small targets.