This 18" wood shelf is 18" long and made of 8" wood, so it measures approximtely 18" x 7.5". Good size for a chinchilla to really sprawl out on, or run around on!  
Would you like a hole in your shelf? Be sure to select that listing as well and add it to your cart!
Better picture coming soon... bolts can be installed however you want -- long side, short side, one long & one short, and so on...
 
Which side do you want the bolts on? Short side? Long side? Both? Custom?