The documented job is “How to Clean Concrete, Brick, and Block Before Coating or Repair — The Complete Guide”.
✕DO NOT FORCE THE FIT
Soft, delicate, or crazed glazes as a default — it can score them; start with nylon or brass and escalate only if needed, with a test patch.
Broad flat fields — the 5/8" grout face is narrow on purpose; open areas want a scrub block or stripping brush.
Contaminating stainless-critical work — as a stainless brush it's fine on masonry and tile; if you also keep it for stainless-metal work, don't cross-use it on carbon steel (the dedicated-brush rule).
Everything about the fine-grout-brush technique applies
stay in the joint, track the wire down the line, let it work the raked profile — but with stainless the "stay in the joint" rule is a glaze-protection rule, not just an efficiency one. Use light-to-moderate pressure; leaning doesn't help stainless cut grout much and only raises the risk of the wire skating onto a tile face. Let a cleaner soften mineral deposits and re-apply rather than grinding dry. Because it's the hardest brush in the trio, it's the one most likely to leave a mark if abused — so it's the escalation tool: reach for it when brass has failed, test first, and back off the moment the joint is clean. Unlike a carbon brush, it won't rust in the wet work, so it needs no drying ritual for corrosion — though rinsing debris out keeps it cutting.
Asked at the counter
BUYER QUESTIONS ANSWERED BEFORE THE CART, NOT AFTER THE RETURN
Stainless or brass grout brush?
Stainless (this one) is the aggressive tool for hard, stubborn grout; brass (46811) is the gentler, glaze-safer step. Start softer and escalate.
Will it scratch my tile?
It can — stainless is harder than a soft glaze. Keep it in the joint, test in a hidden spot, and don't use it on crazed or delicate glazes.
Can I use it on efflorescence?
Yes — dry-brush the salt bloom off first, then treat; never seal over active efflorescence.
Does it rust?
No — it's stainless, made for the wet, chemical grout/masonry work that would rust a carbon brush.
Why does one listing say 1/2" × 5-1/4"?
That's crossed copy from a stripping brush; the grout face is 5/8" × 2-1/4" per the catalog (pending physical confirmation).