The Mexican red knee tarantula is coloured black with brown hairs across most their body. At the leg joints are the red bands from which their name is derived. Their carapace is beige with a black square at the centre. The upper section of the leg is orange. The leg span of the red kneed tarantula is 15-17cm (5.9-6.7in). Their weight ranges from 15-16g (0.5-0.6oz). The genders appear similar but males do have a slightly smaller body and longer legs.