Refractometers

By far the best product for this job. Period. I already own a strong, and was looking to add a 2nd one. Based on the recommendation of a reviewer on the strong page of magnet strength being equivalent, I opted to go with the long instead. After all, why pay more if there's no noticeable difference? My experience has been very different in that there is a significant difference in the power of the magnets between these two. Perhaps this difference in experience comes from the thickness of the glass but on my reefer 450 front glass (15mm), there's no question that the strong is considerably more powerful and worth the additional $$$. Having said that, fresh blades make an even bigger difference. The long with new blade was better than strong with old blade -- so make sure you replace them with a fresh set every now and then. Not sure how often that should be -- my current one had been in use for approx 2 years. I kept them clean so didn't think they were worn, ...