Comment by altairprime

The Jetstream Edge pen uses the same SXR refill size as the 4 colors of refills for the SXE3/MSXE5 multicolor pens; while their website only lists 0.28mm and 0.38mm refills as compatible, the SXR-80-05 refills are also compatible. But I suspect the reason they’re not formally listing 0.5mm support is because the lower-capacity SXR runs out of ink too rapidly when used in single-color 0.5mm, and so that’s why they cap the pen at 0.38mm. Recommend avoiding these as an option.

However!

The SXN-150 and SXN-155 lines deliver normal capacity 0.5mm Jetstream pens; and their SXR-5 refills deliver single-color 0.5mm Jetstream through the SXR-5 refills.

https://www.mp-uni.com/vn/en/product/jetstream-sport-sxn-155...

https://www.mp-uni.com/sg/product/refill-sxr-5/

You can search for the often-dehyphenated SXR-5 refill compatibility to see what pens they fit besides the official SXN-150 options (like, for example, the Pentel Energel); MP’s own website isn’t listing the options properly on the refill page — they only list the SXN-155/S and not the SXN-150/C, for example — so some footwork would remain to identify precisely which official model numbers are associated with the 0.5mm refill — e.g. the SXN-150 and SXN-157 bodies sold at JetPens are all 0.7mm/1.0mm but accept any SXR-# refill for # in { 38, 5, 7, 10 }. I suspect any SXN-xxx* body where x >= 150 is compatible with any SXR-y refill, since the discontinued SXN-100 seems not to be and the SXN-189DS seems to be.

Note that I found it rather difficult to locate the SXN-155 body by model number for shipping to the United States; the UPCs for whichever models you want, e.g. 4902778040737, were much more efficient in locating options.

TLDR: Yes, there are official Jetstream 0.5mm pens and refills, in addition to modding any SXR-refillable Jetstream with 0.5mm yourself.