Astacus leptodactylus can grow up to 30 centimetres (12 in) in length from the tip of the rostrum to the end of the telson (tail), but is more commonly found at around 15 cm (6 in) in length. The sides of the thorax are very rough, usually pale yellow to pale green in colour. A. leptodactylus has two pairs of post-orbital ridges, the second of which may have spines. It also has a prominent tubercle (small nodule) on shoulder of the carapace. The claws of Astacus leptodactylus are long and narrow (hence the common name 'narrow-clawed crayfish'). Their upper surface is rough and the underside is the same colour as the body. A tubercle can be found on the fixed side of the claw. A. leptodactylus can be distinguished most easily from the European or broad-fingered crayfish, Astacus astacus, by the relatively thinner "fingers" of the claws.