Surface radial magnetic field of V374 Peg a) and GJ 1245 B b) recovered with ZDI from spectropolarimetric observations. The field has been reconstructed up to ℓ_max = 10 (4) for V374 Peg (GJ 1245 B). Surface differential rotation of V374 Peg has been derived by Morin et al. (2008b) from spectropolarimetric observations, while this was not possible for GJ 1245 B. Magnetic fields are expressed in units of the square root of the Elsasser number.