Hey,
Quick one this week, written ninety minutes after publishing the ninth product on my Gumroad. I wanted to send the email before I had the data so I cannot retroactively spin the story when the numbers come in.
What shipped
GUM Measurement Uncertainty Budget Toolkit — $19 (English) + ₩30,000 / $22 (Korean edition v1.1)
A 45 KB (EN) / 249 KB (KR) zip file containing: Excel template (.xlsx) with 6 sheets, formulas wired to ISO 10012:2026 + JCGM 100:2008; 11-12 page reference PDF; 4-page KOLAS / A2LA / UKAS audit checklist; README.
For ISO/IEC 17025 accredited calibration laboratories that need to update their measurement uncertainty templates to comply with the new ISO 10012:2026 standard published in February.
If you do not know what GUM is, this product is not for you, and that is the whole point. The previous eight products on my Gumroad were trying to be for everyone and sold to no one in 56 days. This one is for roughly ten thousand specific QA managers worldwide who are currently doing template-update work this quarter.
The buyer of this product has a job title (Senior Metrologist / QA Manager) you can find on LinkedIn, has a regulation update on their desk today (ISO 10012:2026, Feb 2026), knows what JCGM 100:2008 clause G.4.1 refers to without Googling it, and owns the budget for their lab’s tooling without going to procurement. They already have the problem the product solves and are already losing time to it.
Last week’s numbers (build-in-public log)
Medium: 10 articles published, 30 days, 21 views combined.
dev.to: 5 articles in last 24h, 11 views total, zero reactions. Algorithm dampens multi-post-per-day. Going back to 1/day.
Beehiiv subscribers (you): roughly 21.
Gumroad: 8 products archived. 9th (EN) + 10th (KR) just launched.
MCP server invocations: handful, most mine, debugging.
Total spent: about $16 in API fees + 60 hours across all channels.
Two-week experiment
If the GUM Toolkit gets >= 1 sale in the next 14 days (May 19 → June 2), the hypothesis holds and I will build the next domain-specific product.
If it gets 0 sales in 14 days, the hypothesis fails — meaning a $19 calibration toolkit cannot be discovered via cold Gumroad search and needs a different distribution channel (LinkedIn outreach to QA managers? KOLAS conference booth? KRISS direct relationship?).
I will email you the result on June 2 either way.
— YB
Store: kyb8801.gumroad.com
Reply to this email if you work in calibration and want me to know about a feature gap before I build v1.2.