The maximum weight allowed is 30 kg per shipment including packaging. If a product exceeds this weight, it is not possible to ship it via Wallapop shipments.
As for size, if packaged in a box, the sum of the length, height and width cannot exceed 210 cm. Also, the length cannot exceed 120cm. Remember also that the minimum measurements for the package are 15x10 cm.
The weight must be placed by the seller in the ad at the time of uploading the product and only the seller can edit it. If you haven’t stated it when uploading your ad, you'll need to edit the ad and add the weight to make the transaction.
As for packaging, Correos does not allow packaging with advertising from third parties. Boxes must be plain and white or brown. The shipment of irregular products is not allowed either. If the Post Office considers that the packaging is not appropriate for the transport of the product, it will suggest the purchase of the boxes that have an extra cost to the seller.
The preparation of good packaging to protect items and avoid damage during transport is essential and the responsibility of the seller. For more information on how to prepare a good packaging, check this article: Tips for good packaging.