I believe exersice sheets are measured from the whiters to the dock, not from the chest like rugs. I found a conversion table ton a website (horserugsonline.com) which says that for a 6'3 rug, you'd need a 4'9 sheet. Have a browse on the internet for different types - some have filler for cold days, others are thinner and just waterproof. You can also get flourescent ones for hacking. They also come in different styles - some go under the saddle, some over, some go right over your legs for cold, wet days. Some are like rugs and fasten at the front while most are straight-cut from the whithers. eBay is always a good option for saving money.