Dubo retaining washers are manufactured by injection moulding of nylon base material. As the moulds have multiple positions, in theory there could be some variation in the size of washers. However, the moulds are fixed in size, and any variation is within specification. More importantly, these washers are designed to be deformed anyway when applied correctly, so their shapes change completely after tightening with the appropriate torque (see image below). This is necessary for the full retaining effect. The washer spreads around the bolt head and into the thread. The functionality of the washer is not compromised in any way by a slight variation in size.