Despite being primarily defined by the use of a system-on-a-chip of one of the Actions brands[2] usually of the ATJ20xx series and some common core features, S1 products vary widely in software and hardware as well as design (including lookalikes and even counterfeits of other players), leading to a jumble of hard to identify internal designs, all employing non-mutually-interchangeable firmwares.

There are also tools developed by individuals under the Open-Source license, such as s1res ans s1clone[6] that allow the consumer to modify its device by changing bitmaps and text.

Problems have arisen as consumers have attempted to upgrade their players using incompatible firmware with a higher version number.

However, a 'dead' player can sometimes be recovered by opening it, shorting some pins and uploading a full firmware from the PC.

Due to common mold specifications of the player type, this list will never be complete.