Axle tube seals,what size do I need?

I picked up some Yukon Hardcore 27 spline inner shafts for a d30. I also got some axle tube seals. How tight are the seals suppose to fit? Are the outer parts of the Yukon shafts the same size as a 30 spline upgrade because the tube seals are a very tight fit after the shaft tappers up to a larger size. Do I need to get the big spline axle tube seals?

Thanks for the help!