Choose a particular size and handling layout, not a promised finish. The US Ceramic + ion Thermal Round and NanoThermic Round Thermal are both manual brushes for use with a separate dryer. Their names do not indicate a powered heating element. If you already own a round brush whose working surface and grip suit your sections, these overlapping lines do not require a replacement.
Compare like-sized labels carefully
Table: swipe sideways on a small screen, or focus and use arrow keys.
| Exact variant on US listing | Maker's size label | Line feature to inspect |
|---|---|---|
| Ceramic + ion Thermal CI-35 | 1 3/8 inch | Seamless body, vent holes and soft-tip bristles are described on the line page. |
| NanoThermic Round Thermal NT-34 | 1 1/4 inch | Its line page describes a ceramic-coated barrel and its own bristle layout. |
| Both lines | These labels are not equal measured diameters. | Maker lists a retractable sectioning pick; replacement picks are line-specific. |
The maker shows a “Barrel & Bristle Diameters” image on each page. This comparison retains the maker's nominal labels because the image, rather than accessible numerical text, carries the two measurement definitions. It does not convert CI-35 or NT-34 model suffixes into millimetres, or use an outside-bristle measurement as a barrel diameter. Confirm the exact field on the maker image or packaging before comparing a brush with another brand's size label.
Where the practical difference lies
Pick the shape you can turn and release on your usual section. The Ceramic + ion page explicitly describes its seamless body and large vent holes; the NanoThermic page describes its coated barrel and layout. Both pages make claims about styling speed or shine; those are maker claims, not evidence that one line outperforms the other in a matched test. The maker's brush chart shows a retractable sectioning pick for both lines, while each product page says its replacement pick fits only that line. That matters if you expect to service the pick rather than replace a whole brush.
For short face-framing sections, start with the size and working-section guide; if the section cannot take the curve or reach the barrel, a slightly different coating will not solve that geometry. For a dense section, narrow the working section before mechanically choosing a larger diameter. To compare bristle layouts, use the bristle guide; to practise release, use the dryer technique guide.
This is limited to the two named Round Thermal line listings in the US store, checked 11 October 2026. Speed XL, Contour, HeatPro and other lines may have different dimensions or features. No first-person testing, measured drying-speed or equivalent-size claim is made.
Compare the usable surface in person
If you can inspect both exact brushes, place a typical section against each without switching on a dryer. Check whether the section fits along the bristled length, whether the handle turns comfortably, whether the bristle ends grip without collecting adjacent hair, and whether the section can release. Those observations can decide a purchase even when two lines have overlapping coating and vent claims. They are a suggested trial, not a report that we performed it.
When shopping remotely, ask the seller which diameter its number describes. A photograph labelled “1 1/4 inch” may show the brush from a perspective that obscures whether the measurement spans the solid barrel or bristle tips. Keep the maker's CI-35 and NT-34 labels in their own columns until the actual definitions are available. A same-number model from another line is not automatically a matching outside diameter or matching handling size.