Understanding surface finish specifications
| SPI Grade | Ra Value | Application |
|---|---|---|
| A-1 (Diamond Buff #3) | 0.012 um | Optical lenses |
| A-2 (Diamond Buff #6) | 0.025 um | Clear decorative parts |
| B-1 (600 Grit) | 0.05 um | General high gloss |
| C-1 (320 Grit Stone) | 0.18 um | Semi-gloss / matte |
| D-1 (Glass Bead Blast) | 0.35 um | Textured / non-glare |