Cladwell 26 4 DM window balance replacement

Your balance looks compatible with both our S380-27 and S385-27. These two balances are very similar with the exception of the bottom balance shoe. The depth of the bottom balance shoe of the Series 380 measures 1" and for the Series 385, it's 1-3/32". You will need to measure the depth of the bottom balance shoe, like in the diagram below to determine which balance would make the best match. Whichever one you decide on, will use a 2640 option. 

Alternate view of 15-004