The Eclipse CS has a .35mm config and can be configured with a .5mm. As far as i know there is no nozzle, head, needle for the Eclipse series to configure to .3mm.
The HP C+ (plus) and HP CH Hi-line can be configured in a .2mm | .3mm head assembly, are you sure its not the HP C+ (or Plus) that you are seeing offered in addition to the Eclipse?
More can be found from the Iwata Website -http://www.iwata-medea.com/products/iwata-airbrushes/eclipse/hp-cs/hp-cs-specifications/
| HP-CS | Tip Size | Nozzle | Nozzle Cap | Needle | O-Ring | Notes |
|---|
| Standard |
.35mm |
I 604 2 |
I 602 2 |
I 617 2 |
N/A |
– |
| Optional |
.5mm |
I 604 1 |
I 602 1 |
I 617 1 |
N/A |
– |
The HP C+ details - http://www.iwata-medea.com/products/iwata-airbrushes/high-performance-plus/hp-c-plus/hp-c-plus-specifications/
| HP-C | Tip Size | Nozzle | Nozzle Cap | Needle | O-Ring | Notes |
|---|
| Optional |
.2mm |
I 080 7 |
I 140 1 |
I 075 1 |
I 125 7 |
– |
| Optional |
.3mm |
I 080 8 |
I 140 3 |
I 075 3 |
I 725 1 |
– |