I received this from an acquaintance, but I have never used it myself. There are two sets of carriers in total, so it can carry up to 4 skis. The outer dimensions (cross-section size) of the square bar that fits this product are approximately 32 x 23mm, so it should work with THULE and INNO (Carmate). Terzo (PIAA) bars are also approximately 31 x 21mm, so there is almost no difference, and installation is possible. I have lost the inner square bar fixing screws, so I have substituted them with other screws (see the attached images). They are hexagon socket head bolts (M6x15mm), so you can easily fix them with the included hex key (Allen wrench). The items for sale are all in the first photo, but the two sets of parts on the right are bonus items. There is no key. ★I found one key. Please take a look at the image (#10) (the image shows the key attached when locked). ★This product is also for sale on another online shop, so please be sure to check the stock before bidding.