They'll be 48mm Sachs forks.
Typical OC fork. Scary in them. You will need a 48mm seal driver to get the new seals in. The dust seals are TIGHT! you'll have fun getting them out.
ALSO! More than one of us on here has managed to cross thread the rebound clicker in the damper rod upon reassembly. Do a search for the correct method (basically take the clicker out of the cap first, thread it into the damper tube, then put the cap over the top).
KYB 48mm bushing and seal kit can be had for around $50 and includes everything that will fit perfectly! 09 CRF450R (from memory)