The quality is a little suspicious. After about 2 months of use, mine cracked and splintered. It still works but I can say its days are numbered. It's plastic and not hard. What do you see in this picture. hollow ring. Any pressure, like a boat turned on its side a little, will easily crush it and cause it to break. However, these things are cheap. They are usually suitable for flat surfaces and can be easily replaced for little money. The warning here is: don't think this block will hold your…