C3 is ok although you could use a std clearance on that side & C3 on the mag side but they list the same part number both sides, probably to make it easier & less confusing. Here's a random link i googled & i expanded the pic right up & can just see C3 on the inner race on one bearing but both the same bearings.
www.oemcycle.com/Item/product/900000499

Picked up a new bearing today- 6206c3 but this one is manufactured by NTN, does it matter if each side of the case has bearings from a different manufacturer? Also this bearing was sealed, which I popped out, will that cause any problems?
Thanks

Hi, the Manufactor Name doesn´t matter, at least when both come from a well known brand. For me a riddle is the clearance. For a DT400, my origin Yamaha parts cataloge Shows B6306C4 the DT250 is written B6206 without mentioning any clearance. As the DT400 bearing is only 1mm bigger in outside Diameter, why should the DT250 bearing have a C3 clearance and the DT400 a C3? But just a guess, not sure. Have 2 crankshafts but on None of the 4 bearings anything is written to compare.