Flap discs produced by Sia may look the same to others on the market but when we have tried these with a few of our customers the feedback was in favour of Sia's flap discs when comparing as close to a price to price basis as possible. Sia themselves have 3 grades of flap disc and possibly the best all rounder is their 'Standard' disc (also referred to as Stingray). However if you are looking for the longest possible life from a flap disc then the 'Jumbo' (also referred to as Salmon) disc is the best there is. 
Noz-Alls estimate 993mm of abrasive media on the Eco, 1432mm on Standard and 1941mm on Jumbo flap discs. 
68 inserts on Eco, 80 inserts on Standard and 110 inserts on Jumbo.