Those Shimano pedals will accept 6mm allen wrench on the hind-side, and a standard 15mm wrench. If you've left the pedals alone (ie. never serviced) bet you'll have a tough time with the allen wrench due to lack of torque on a 6mm wrench.
Best option is pedal wrench, but use care not to accidentally fiddle with the lock-nut.
Those Shimano pedals will accept 6mm allen wrench on the hind-side, and a standard 15mm wrench. If you've left the pedals alone (ie. never serviced) bet you'll have a tough time with the allen wrench due to lack of torque on a 6mm wrench.
Best option is pedal wrench, but use care not to accidentally fiddle with the lock-nut.