Sandisk Extreme speeds

Hi all,

I’ve never used MicroSD cards before but I bought a SanDisk extreme 128 to use with my SP3 to free up some space. I’m finding the speeds not as fast as I expected and it varies significantly. It was less than 1MB/s (100KB/s) but has gone as high as 75MB/s. For the most part, though I’d say it averages maybe 20-30 (between the extreme highs and extreme lows)? I tried it on a different laptop (XPS 13) and was getting the same speeds. I ran crystaldiskmark and got 90BS/s read and 80MB/s write

Is this right? thanks