Spriing arch support kits (including shells and short covers) come in full sizes (not half sizes). We recommend going with your SMALLER shoe size if you are a half size or fluctuate between sizes. If you are a half size, for example 8.5, always go DOWN in Spriing arch supports, in this case, a size 8. If you fluctuate between shoe sizes 8 and 9, go DOWN in Spriing arch supports to size 8. Because Spriing shell sizes are directly related to arch length, another useful tip is checking if you have long or short toes. If you have long toes, your arch will be shorter (size 8). If you have shorter toes, your arch will be longer (size 9). If you aren't sure, or your toes are just mid-length, just stick with the smaller size (size 8).