To determine which size of track you need, Seldén has developed a Main Sheet Track Calculator which is available on-line. You will be asked to fill in your boats Righting moment at 30° heel - no worries - there is a calculator for that too. 

https://support.seldenmast.com/en/services/calculators.html

TThe System 30 Main Sheet Track Assembly is designed for yachts up to 45'. It features a 4:1 purchase and cam cleat controls integrated in the end controls. The kit includes:

• Main sheet car 443-181-01. The car is black anodised, extruded aluminium and runs on Torlon® ball bearings. It features plain bearing polymer sheaves for control lines and an AISI 316 mirror finished stainless toggle for Seldén PBB 60, PBB 70 and RBB 60 blocks. The toggle and sheet block are supported by a rubber stand-up collar to improve function and to dampen vibrations.
• End controls 443-112-02 / 443-112-03 with Size 38 mm cam cleats. Plain bearing sheaves and an integrated becket for the control line. Rubber shock absorbers prevent damages on car and end controls. 
• 30 mm hard anodized standard track for M6 screws. Hole distance is c-c 100 mm. Length 1500 mm.
• 9 m control line, 24-plait Polyester.
   

Length: 1500 mm
Max MSL: 40.00 kNm