Last week, Microsoft released Windows 10 Insider Preview build 17758 to the Slow ring, and today, the firm is offering ISO images for the build, for those that want to do a clean installation. It's the fourth Redstone 5 ISO to be offered, replacing build 17744.
The ISOs being released today is the latest build that's available in the Slow ring, as it was made available on Friday. We're at that point in the release cycle now when builds are coming in rapidly. This is apparent in the fact that there were two builds last week released to the Slow ring.
The Windows 10 October 2018 Update will be released in, you guessed it, October. That means that Insiders will see an RTM build very soon, possibly even this week. After that, things should move pretty quickly. That build will be promoted to the Slow ring, and then to the Release Preview ring, before being made available to everyone.
If you want to download the ISOs for Windows 10 build 17758, you can find them here.