Made in a hyper eutectic alloy with a high silicon content to provide tight cylinder clearances and quiet running characteristics, manufactured by a world class piston manufacturer to "MAR Motorsport specification" uses an optimised crown and dish (9cc) shape for improved swirl/burn. The A-series always gives better performance with a larger piston dish and smaller chamber volume. It also means that an otherwise standard 1275 cylinder head and engine block the bore size increase can be used initially where required as there is no big problems with compression ratio. These are totally different to the original Evolution piston stocked pre 2012.

Top ring is 1.15mm, Chrome face Second ring is also 1.15mm height Oil Rings are 4mm

For the ultimate in engine performance, these pistons, installed in a 1275cc block, will blow your doors off! You can't beat cubic inches for performance, and the A-Series block can be bored far bigger than the factory ever imagined. The stock bore is 70.6mm, the 1380 bore is 73.5mm. This is .120" oversize and still leaves room in the block to go to 74mm (1400cc), but only if you offset bore prior to going to 73.5mm. These 73.5mm pistons from Nural (Federal Mogul) are great for street and mild racing.
Top ring is 1.47mm height
second ring is also 1.47mm
Oil ring is 4mm in height 73.mm bore size is 2.8973", Pin height is 1.4875. Top 2 rings are 1.5mm height (.0591"), oil ring is 4mm (.1575")
Pin Height- 1.47"

When Omegas supply of A-Series pistons became bad Mini Spares took it upon themselves to design and build a better Piston. These super high-quality FM-B2 cast pistons ensure the alloy has the best molecular consistency which enhances the strength and performance and double heat treated are manufactured by AE (Federal Mogul)and are available only from Mini Spares and their distributors. Pistons are available in conventional 1275 oversizes (+.020, +.040, +.060) in both flat-top (C-AJJ3382/size) or dish (C-AJJ3378/size) configuration, and in dished 73.5mm "big bore" configuration for 1380s (C-STR310). These pistons should prove to be bullet proof! Desperately inconsistent supplies for protracted periods of performance Mini pistons caused Mini Spares Centre to develop the 'MEGA' piston range. Recruiting the AE Hepolite Group for their unquestionable and renowned design and manufacturing expertise, the goal was to produce the most robust piston possible given reasonable cost and weight limits. Applying current technological advances incorporating their very latest hi-spec FM-B2 double heat treated lightweight alloy and special double heat treatments, the result is an extremely durable piston that will withstand greater cylinder pressures at higher rpm than any other currently available. To simplify the range, material has been concentrated around various problem areas - the ring lands and crown - providing one crown height which is 1.2mm thicker than other leading manufactures. This ensures sufficient material in critical areas to allow machining where long stroke cranks or longer con rods are used. This design guards against premature damage from poor/low quality modern fuels with the rings re-sited to minimise detonation damage in high compression engines. Thr ring dimensions are compatible, and therefore interchangable, with the early Omega Mini piston range. Full circle skirts are used for maximum piston and ring stability. They also feature a specifically designed ridged finish on the side of the piston walls which helps retain oil, to protect against scuffing and galling at start up and cold running. A tapered gudgeon pin is employed to maximise stiffness against its lightweight. The piston ring groove design has stepped away from convention, utilising specs distilled out of intensive testing and are as used on the very latest high-performance pistons for mega-powered Japanese engines. Suggested finished honed bore to piston clearances are as follows - Road/fast road - 0.0015 to 0.0017" Sports/super sports - 0.0018" t0 0.002" Race - 0.0022" to 0.0025" Turbo road - 0.002" to 0.0025" NOTE - The piston rings are position specific and the second compression rings are directional. The top ring has no directional markings. The second ring has a small dot stamped in to it. This is to be fitted with the dot facing the top of the piston. AE Hepolite is now owned by Federal Mogul and trademarked "NuraL" Gudgeon Pin to Piston Crown Dimension 38mm +/- 0.05mm.