If you are struggling to find the right headboard, or suffering back pain from the hardness of the bed's back wall, this Backrest Bed Wedge Headboard Reading Pillow is an excellent choice. Without installation required, it provides soft but sturdy back support when you're sitting up in bed for reading & watching TV, not easy to slip or collapse. It has varied standard sizes to fit across all standard beds and can accommodate multiple people at the same time. The pillow cover is removable for washing purposes. The standard sizes(WxHxD) are Twin 39"x20"x8"(3 buttons), Full 54"x20"x8"(4 buttons), Queen 59"x20"x8"(5 buttons), California King 71"x20"x8"(6 buttons), King 76"x20"x8"(7 buttons). The twin-sized reading wedge back pillow is popular among back to school students, while the king-sized can convert a daybed/twin bed to a couch/sofa. * The green colour is in a very slight and tricky tone, if you expect it to be a general green, please DO NOT purchase it. Meanwhile, you have to open the compressed transparent packing bag to judge the green fabric in person instead of simple looking through the bag. Thanks for your kind understanding!