These super duper wheels are well and truely fab!! we had one for our british shorthairs and they all loved it! super sturdy with no derailments and they don`t sound like a london tube train rolling into a station like our first ever wheel of a different brand did😝 the larger than average wheel diameter ensures there is no harmful spinal compression during use. these wheels are great for indoor and outdoor cats alike and provide great mental and physical exercise,they are also great for small dogs! They currently retail at £456 each and you could win one for just £5 with Safecat UK catios the wheel is 51" diameter and 12.5 " deep full material and size specifications can be found on cazami cat exercise wheels facebook page