The plastic bag of the supermarket store Mercadona is a rare symbol. It looks like a "stop" symbol with the letters SPB inside. It took my attention and I searched internet about it. I found some references to the Mercadona page, in different languages: Ventajas: SPB. Siempre precios bajos. Nuestros productos están Siempre a Precios Bajos. Ahorro en la suma total de la compra, porque el cliente paga menos ADVANTAGES: SPB. ALWAYS LOWER PRICES. Our products are Always at Lower Prices. Saving in total shopping, because the customer pays less for each ... AVANTATGES: SPB. SEMPRE PREUS BAIXOS. Els nostres productes s'ofereixen Sempre a Preus Baixos. Estalvi en la suma total de la compra, perquè el ... I have not figured out if it's true, I think it depends on the product of the season, etc. etc. But truly the bags are a world full of surprises. I have discovered a decatholn plastic bag (one of thousands I mean). Is said that the bas can support up to 10 Kelvin grams. A number of unusual for a weight, what do you think?