Comprados para usar en pizarra blanca Ofitura 60x45. Trazo medio (ni muy gordo ni muy fino) funcionan perfectamente después de 2 meses, eso sí, hay que seguir las instrucciones tanto del rotulador como de la pizarra, leáse:antes de borrar, dejar que se seque bien el trazo escrito (lo facilita este rotulador) / el fondo de la pizarra, es muy importante que se mantenga limpio ( no cada día, pero yo, una vez a la semana la "repaso" con un producto especial para pizarras blancas ) / no dejar trazos escritos muchos días sin borrar / utilizar un buen borrador para este tipo tinta (yo compré el Bi-Office AA0105 )Por favor si te ha servido mi opinión dale al botón de "Útil" muchas gracias.I was so excited for these pens as I was relying on the for my revision. They come in a lovely range of coloursand write really well. HOWEVER, when it came to wiping them off I couldn't remove the pen marks. First time using them and they have completely ruined my whiteboard, thus leaving me without a whiteboard or a pen and I desperately needed to revise. I'm left extremely disappointed as I expected more from Bic.I bought this product to write lesson note to my students but I can't use it because the chemical odour is too strong and makes me feel sick and my music studio smell feels like a car garage. They don't mention that this product is odour free, so I suppose I can't complain but if you don't want the. smell, I would recommend to find different product. I will not buy this product again.They stench like I don't know what in addition to it they are very difficult to clean. They leave some sort of grey stains which are very are practically permanent. Destroyed the whiteboard on which it was used.I'm a nurse and wanted to stock up on white board markers as can never find one when I need one. I was chuffed with my new pens, they write beautifully so I diligently and neatly rewrote all the name and patient info boards for the whole ward... then when it was time to clean a name off we realised that it doesn't come off! It leaves a shadow stain on the board that didn't come off with hard surface wipes, alcohol gel or chlorine. Ended up using acetone to remove it which took forever. Never again!