If you have bought something online or from a catalogue and it gets sent through the post, you expect it to arrive in mint condition. Therefore, when you are sending anything out yourself, you should do the most you can to make sure it arrives the same way. Obviously if you are sending larger items then you are going to need to send a box filled with cushioning material such as packing peanuts or bubble wrap. If on the other hand you are sending something smaller then you may find that it is better to use padded envelopes to protect your item.
You will find that you can get a variety of sizes to suit your requirements so it depends on what exactly it is that you need to send. If you are sending smaller items such as jewellery or maybe a watch then there is no point in you purchasing the larger varieties. Similarly, if you are sending something such as a CD or a framed photo then you need to make sure that there is ample room for them to fit in. You don't want to have to squeeze your items in because then there is more chance of the packaging splitting and damage occurring.
Most of the padding is provided by bubble wrap being attached to the inside wall. This means that not only is your item giving a soft cushioning but it is also a lightweight cushioning. The weight of the delivery package is important because you will be paying more for heavier parcels. If you have any items that need to be sent that could possibly be broken in transit but don't really require a large box then padded envelopes will more than likely be your best option. They provide good protection for your package and are lightweight option so should definitely be considered.