However, [DVD-RAM]'s not compatible with most drives and players (because of defect management, reflectivity differences, and minor format differences).

Single-sided DVD-RAM discs come with or without cartridges. There are two types of cartridges: type 1 is sealed, type 2 allows the disc to be removed. Discs can only be written while in the cartridge. Double-sided DVD-RAM discs were initially available in sealed cartridges only, but now come in removable versions as well.