Stainless Steel is a higher quality material and as a result is more expensive, and from a manufacturing volume point of view less common than the standard steel models. Unfortunately the lower volume and more costly material increases the overall cost.

Unfortunately we cannot supply extra keys for this unit. However a local key cutters shouldn't have any issues duplicating your current key.

This post box is anthracite grey- RAL 7016.

The aperture may allow small parcels to be deposited but is really designed for standard post. We do offer the Black Parcel Post Box which may be more suitable should you wish to consider this.

The potential for water ingress will be dependent on how exposed the box is to the elements, if this is to be located somewhere that is not particularly sheltered you could consider the Brabantia - B100 Dark Grey Post Box as this has flap covering the deposit aperture.

No, the B410 is a larger post box and the holes are spaced differently.

I would always use the rubber seals if the post box has a chance of getting wet just to protect your mail. Installing the item without the seal would not invalidate the warranty.