What is the difference between dlink dir 600L B1 and dir 600 B1

Do anyone know what is the difference between this 2router.

I don't see anything that suggests the L variant is supported by OpenWrt.

The 600 B1 is only a 4/32 device, so it's not able to run anything modern... don't even bother with it.

But is there a reason you're asking this again?

I know but ddwrt support that if 600 and 600l are same i will install that on 600L router which i have as this is now a e waste if that device can be used by installing something .

I would recommend e-wasting these devices -- running an old version of OpenWrt will be a security liability and will have generally poor performance.. But if you want to install DD-WRT, ask on their forums for compatibility and to ensure that your devices can run an up-to-date version that will not be a security risk.