The Canon Eb eyecup is supplied with many of their SLR cameras as standard equipment, providing effective cushioning and shielding of stray light.
EB is for:
Canon EOS 50D, 40D, 30D, 5DII, 5D, 60D, 5D2, 60Da, 6D.
EF is for:
Canon EOS 550D, 500D, 450D, 400D, 650D, 600D, 700D, 1100D
DK-20 is for:
Nikon D3100, D5100, D60, D3000, D3200, D500
DK-21 is for:
Nikon D200, D80, D90, D70S, D70, D7000, D600, D610
DK-24 is for:
Nikon D3000, D5000