The Amstrad DMP2000 Printer 8K Buffer Kit from Goldmark Systems is a RAM upgrade for Amstrad's DMP2000 and DMP3000 printers.
The "kit" seems to be simply consisting of a 8K SRAM chip, to be used as replacement for the printers built-in 2K SRAM, increasing the buffer size by 6K.
The kit doesn't seem to be required for newer DMP printers - according to LQ3500di and LQ5000di Leaflet (English) and DMP3160/DMP3250di/DMP4000/LQ3500/LQ3500di/LQ5000di AMSTPRINT Leaflet (Norwegian) - these do already have 8K Buffer RAM built-in.
According to german DMP service manuals, only DMP2000 and DMP2160 have 2K RAM (where the upgrade would make sense). Whilst DMP3000 and up do already contain 8K RAM built-in (so the upgrade wouldn't make any sense).