This is a windsurfing extension. It's an aluminum extension, and the manufacturer is Liberty. It's compatible with SDM masts (the thicker type) and fits pin-type bases. It has three pulleys, so it can accommodate sails with a 4-pulley setup. It's made of aluminum and has a substantial weight to it. It looks quite sturdy. It comes with lines, so you can use it right away when it arrives. Please judge the condition based on the photos! If you need any other information, please send me a message. Shipping is set to be paid by the buyer, but I can also ship it with the shipping costs prepaid. The shipping fee will be charged separately. I can accommodate your preferred shipping method, so please feel free to ask! Regarding price negotiations, I will consider them if you purchase other items together. If there are any other items you want, please send me a message, and I will look for them! Thank you.