ak mags compatibility

[kakitli]

Hi all,i've just bought a Cyma RPK and a ak74u.I bought some second hand mags for it i don't know what brand but they don't seem to fit.I realise the top of the mags the length is different.One is longer than the other.
Here are some pics:








the all brown one is little bit longer than the brown/black one,i think thats why it won't holding properly causing not feeding sometime?
Please help.