To ensure professional grade quality, look for suppliers whose products comply with the World Squash Federation (WSF) specifications. For safety and environmental compliance, especially for the EU and US markets, ensure the rubber materials meet REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) and RoHS standards to guarantee the absence of harmful phthalates or heavy metals. ISO 9001 certification of the manufacturer is a strong indicator of consistent production quality.