Have no idea about the spider, but my guess is that a Hollowgram spider won't work with a SRAM arm - I briefly remember the engagement tooth pattern from some X1 cranks I had, so I understand where your coming from, but the SRAM spiders slot on and have three screws to keep them on rather than having a Lockring
Si arms are 172.5mm
Have no idea about the spider, but my guess is that a Hollowgram spider won't work with a SRAM arm - I briefly remember the engagement tooth pattern from some X1 cranks I had, so I understand where your coming from, but the SRAM spiders slot on and have three screws to keep them on rather than having a Lockring