NAPA & WIX are made by DANA-SPICER. The last 4 base #'s are always the same ie:51515 or 1515. Napa uses 4 #'s Wix uses 5. I'm the Parts Mgr. for a large County Fleet Management Department. We have used both FRAM & WIX for years on all of our equipment.TC33D,TL100,8610,JD544G,Gradalls, etc...22 years and not a single problem. They meet or exceed mfrs. specifications. You would be surprised at all the OE part #'s that cross. Go to WIX.com And check it out for yourself. They give micron ratings, relief settings, bypass, etc...