Size and weight of "brand name" packs doesn't always mean they are smaller and lighter. However, Thunder Power packs do tend to be a bit smaller and lighter than most other packs. On the other hand, comparing a "cheap" 2000ma 3 cell lipo pack to a 7 cell 1000ma nimh pack they tend to be the exact same weight in the comparisons I've done. What this means is double the capacity and a higher voltage than a nimh without any gain in weight or size. This can be a good thing for planes that have sensitive centers of gravity or don't have the room for you to adjust the battery position to correct it. For the most part you can mount the lipo right where the nimh/nicad pack used to be and COG should be perfect or very close. Regardless of all that, Thunder Power packs are about double the price of a "cheap" pack with the same specs and I personaly don't think it's worth the price to save a bit of weight. The difference in performance and run time between a nimh/nicad pack and a lipo is such a great step up that I'm not going to worry about paying double to save a little more weight.