Emerson TEC3000 longer lasting 600mAh battery replacement
Replacement Emerson TEC3000 battery, rechargeable 600mAh battery for cordless telephones, this 600mAh battery is longer lasting

This 3.6-volt cordless telephone battery fits loads of phones, far to many to list here, but here are a few examples

Answercall: CT100, Answercall: CT500
Audioline: CDL500, Audioline: FF555, Audioline: FF788, Audioline: FF893
BT: Freestyle 50, 60, 65, 70, 75, 80, 90, 100, 120, PT100686, 130, 300+, 320, 320+, 520, 1025, 1050, 1100, 1200, 1500,
BT: Quartet: 1000, 1100, 1500, 2010, 2012, 2015, 2020
BT: Verve 100

Battery Type: Ni-MH
Battery Voltage: 3.6-volt
Battery Capacity: 600mAh longer lasting version
the size of the battery is 42.64mm x 30.00mm x 14.45mm

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 between charges.