The Alpcour 4-Tier Riser Block is a high-quality training accessory designed for cycling enthusiasts. Made from durable, premium plastic material, this sturdy riser block can comfortably support riders weighing up to 330lbs. Designed to be universally compatible, it accommodates a wide range of tire sizes, including diameters of 26"", 650b, 700c, 27.5"", and 29"" and widths from 23"" up to 29.3"". This wide compatibility makes it ideal for both road and mountain bikes. The Alpcour riser block features an anti-skid design, enhancing safety and stability during high-intensity training sessions. The anti-skid pad at the bottom also prevents any damage to your floor. Each purchase includes a riser block and an extender for those who want to simulate mountain climbing experiences. Additional extenders can be purchased separately for even more climbing scenarios. Alpcour takes pride in the thoughtful design of their products, prioritizing both quality and safety. The robust construction of this 4-tier riser block ensures it can support heavy weights without breaking, and the anti-skid pad enhances overall stability. Elevate your indoor training experience with this versatile and dependable bike accessory.