I wonder if our resident blade geek @ShavingByTheNumbers could throw some light on the subject.
Are you there Grant?
I'm here. I haven't finished making measurements of the Astra SP due to the addition of mass measurements, so I bought a couple extra packs to measure and take care of that, but I have measured the other dimensions. I've measured 24 Astra SP samples so far, so I can safely give you good thickness and width measurements. The Astra SP has an average thickness of 0.090 mm, which is within the normal range for blades, but on the low end, and an average width of 21.94 mm, which is slightly below my current running average across different blades. With the possible exception of a little more blade flexibility that some users might like with the Astra SP in the PAA Bakelite Slant due to the blade thickness being on the thinner side, I don't think that we can attribute the Astra SPs nice qualities to anything special with respect to dimensions. If we look at our ShaveWiki table for blades, we find that it's considered one of the smoother blades with a user rating for smoothness of 8.4. Sharpness comes in at 7.7, which is not our lowest or highest rating so far among blades. I'm willing to bet that there are other blades that are just as good or better than the Astra SP with the PAA Bakelite Slant, but the Astra SP is such a popular blade that it gets a lot of attention. It's not fair to others.