TWRP: File is bigger then Target device

Some how it double posted im sorry.

TWRP: File is bigger then Target device

So i need to flash a cust.img through recovery because fastboot doenst work gives me "remote:command not allowed fastboot" but if i want to flash it through the recovery it says "Error: File larger then target device" i basicly only need to flash the cust.img to fix my phone.

What i tried:
Use fastboot, tried new version of android SDK
flashed diffrent recoverys, same results.

Please help i really need my phone ;/