YSS ‘Pro-X’ 285mm Performance Shock for Piaggio Zip 50 – 100cc / Vespa ET2 / ET4. Has your rear shock seen better days, but you don’t have the budget for a super flashy replacement? The YSS ‘Pro-X’ shock is maybe the best value for money shock we sell. Not only does it offer significantly better performance than the stock shock, but also adjustability via 5 different levels of spring preload which can be easily changed via the supplied tool. The durable black finish wont attract too much attention, and will keep it looking great.