This is an old post, preserved for reference.
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We have updated the design of the 8K cartridge PCBs for the C64 and C128 again. Now with extra shinny gold plated edge connector.
TFW8b cartridges cases.
an earlier version of the PCB, but you can see the various sizes.
2022 Update: More recent versions of the C64 cartridge PCBS are available from The Future Was 8 bit