iPod-4th generation battery replacement 3.7v 750mAh.
Replacement iPod-4th generation battery pack, rechargeable 750mAh Li-ion 3.7v batteries at low prices direct from warehouse

Charge your new battery upon receipt and before you switch on your IPod, if you do not use your device for long periods then a top up charge every 6-weeks should keep the cells fresh and of course do not store away in a discharged state

• iPod 4th generation battery

This compatible 3.7-volt battery will replace the following codes
616-0183
616-0206
BPD1074
AIP-135L1
616-0215
AW4701218074
ICP0534500

Battery type - Li-ion
Voltage - 3.7-volt
Capacity - 750mAh

Fits iPod 4th generation:
M9268CH/A
M9268KH/A
M9268*/A
M9268TA/A
M9282CH/A
M9282FE/A M9282J/A
M9282KH/A
M9282LL/A
M9282TA/A
M9282X/A
M9282*
M9282*/A

My battery has a different Ah, is it still OK to use yours?
The Ah (Amp Hour) Rating is the storage (or fuel) of the battery, the higher it is the longer the battery lasts between charges, bit like petrol in your car so a higher or lower one makes no different to the performance, just the length of time you can use the tool for.

The physical size of this iPod 4th generation battery replacement is
Length - 50.2mm
Width - 36.34mm
Height - 4.62mm