i dont know the dimensions compared to the optima but i made a switch last year from a red top to a die hard group 35 battery, i just like the idea of the warranty which ive used once already and it has been very reliable before i used the warranty (which is a story in itself of why the battery failed but it was my fault not the batteries)...i've tried pretty much every other off the shelf batteries and im done with optimas...if i were to go back to a dry cell i may give the odyssey batteries a look again its small (very small) and a dry cell