What is The Physica Trim To Fit insole? The Physica trim to fit insole is a premium level sports orthotic for use during physical activity. Featuring anatomically superior fit & premium shaping, the Physica basic is ideal to be used in heel heavy exercises such as running. New runners are at the greatest risk in terms of injury, often due to poor muscle value in the lower limbs & lack of technique. The Physica Basic Insole will allow new runners to cover the miles needed to strengthen their body without creating large amounts of impact on the heel, which can take the force of up to 8 times the body weight with each strike. By absorbing this impact, the Physica Basic Insole will allow you to run farther, get fitter & train without the pain. When can I use them? The Physica trim to fit Insole is fitted with the Pedix heel support system which provides maximum comfort during use. This makes the Physica Basic insole the ideal candidate for use during heel heavy exercises such as road running or circuit training. Which size do I need? Available for European shoe sizes 39 to 46. Please choose your European foot size when ordering. Equivalent UK & US shoe sizes are as follows: To fit UK/US Sizes : MEDIUM 39 (UK-6 / US-7) 41 (UK-7 / US-8) 43 (UK-8 / US-9) LARGE 44 (UK-9 / US-10) 45 (UK-10 / US-11) 46 (UK-11 / US-12)