My understanding of low drain vs. high drain is that low drain were optomized for long-term low drain use use without corrosion at the expense of maximum current drain, while high-drain were optimized for high drain, at some expense to best corrosion resistance in long-term use. Most sizes in quality brands no longer distinguish between high and low drain, and the watchmakers I've talked to about it consider it safe to use a quality high-drain battery in a low-drain application.