I was told I HAD to have them to hunt Coues deer in Mexico last year so I pulled the trigger. I already owned the EL Range 10s, 12s and the ATX 95 but figured 15s wouldn't hurt. What I found is, there is a very small window of use for me personally with 15s (500-1000yards-ish) anything under 500 I felt over glassed and over 1000 I wanted my spotter to pick things apart. I could never get them focused well enough to not feel nauseous after 1 minute of use. Over 5 days I MIGHT have looked through them 10 minutes in total. With 10s and my ATX 95 I spotted a fair amount of deer that were missed by guys using 15s. I spotted a few bucks at 1.5-2+ miles that I physically could not see with 15s. I personally do not have a use for 15s and realized they are NOT necessary for long range glassing Coues deer if you have a spotter. I understand they have their use for folks but I do not like using them and will not be using them in Mexico this year.