I have both on several guns. The Scalarworks is slightly lower but a good bit more exspensive. I have also used the MONSTRUM on several Mossbergs. Unsure if they make them for any other guns but they are as low as the Scalarworks and about as cheap as the Sumtoy. I did but new/better screws for the Monstrum as they come with some pretty soft screws.
Ridge Rooster