One of the most common questions when ordering solar mounting clamps is: what frame thickness do I need? Choosing the wrong size can lead to loose panels, installation delays, or even safety risks. This guide explains the four standard frame sizes and how to identify which one you need.
| Frame Thickness | Typical Panel Type | Common Applications | Market Share |
|---|---|---|---|
| 30 mm | Small-format residential | Older panels, some residential | ~10% |
| 35 mm | Standard residential | Most residential rooftop systems | ~30% |
| 40 mm | Large-format / commercial | C&I rooftops, ground-mount, export markets | ~45% |
| 50 mm | Bifacial / double-glass | Large-scale commercial, utility projects | ~15% |
40 mm is currently the most common frame thickness worldwide, especially for panels manufactured for export markets. If you are sourcing for an overseas customer and are unsure which size to order, 40 mm is the safest default choice.
Measuring the frame thickness is straightforward. You need a ruler or a caliper.
| Frame Thickness | Mid Clamp Model | End Clamp Model |
|---|---|---|
| 30 mm | MC-30 | EC-30 |
| 35 mm | MC-35 | EC-35 |
| 40 mm | MC-40 | EC-40 |
| 50 mm | MC-50 | EC-50 |
Each clamp model is designed specifically for its matching frame thickness. Using a 35 mm clamp on a 40 mm frame will not provide sufficient clamping force. Using a 40 mm clamp on a 35 mm frame may over-tighten and crack the aluminum.
Brazil's solar market added 10.6 GW in 2025, with 73% from distributed rooftop installations. 40 mm frames dominate this market, especially for commercial and industrial rooftops. Some residential installations still use 35 mm panels.
The Australian market primarily uses 35 mm and 40 mm frames. Residential systems tend toward 35 mm, while commercial installations favor 40 mm.
European installations are split between 35 mm for residential and 40 mm for commercial. Bifacial panels with 50 mm frames are growing in popularity for ground-mount projects.
Utility-scale projects in these regions increasingly use 40 mm and 50 mm frames, driven by larger-format, high-wattage panels.
Most standard mounting rails can accommodate all four frame thicknesses. The key variable is the clamp, not the rail. A quality mid clamp or end clamp is designed to work with any standard C-channel or U-channel rail as long as the frame thickness matches.
If you are unsure about rail compatibility, check the clamp's slot width and compare it to your rail's slot. Most aluminum solar clamps are designed to fit the standard rail slot width of 18–22 mm.
Can I use 40 mm clamps on a 35 mm frame?
No. The clamp will be too wide and will not apply even pressure to the panel frame. This can lead to the panel shifting under wind load.
Can I mix frame sizes on the same installation?
Yes, but each row should use clamps matching its specific frame thickness. Do not mix frame sizes within the same row.
What is the most common frame size for new installations?
40 mm. It has become the de facto standard for residential, commercial, and ground-mount installations worldwide.