there are 2 types, one each for single sided and for double sided racks.

there is one design, but with 4 choices of height. They are all made with a series of holes (vertically, every 50mm), so that the arms can be attached (with bolts), at different heights, so that you can chose the best position for your needs.

there is one design, but with 3 choices of length (span).

only used with double sided racks, to connect pairs of uprights.
There are 2 types;
With the 620mm connector, unless the arms are staggered at different heights on each side, there is potential for riggers to clash. The advantage of this type is that the overall width of the rack is minimised.
With the 1,180mm connector, arms can be the same height on both sides, and riggers will not clash. This type is recommended for places where there is sufficient space..

there are the following types;

• A basic 700mm long square pipe (50mm x 50mm) that has been welded to a steel back plate.
• A basic 800mm long square pipe (50mm x 50mm) that has been welded to a steel back plate. This is useful for 8s and other wide boats.
• Both basic arms have an extruded rubber top to protect your boats.
• A heavy duty 800mm long square pipe (50mm x 50mm) that has a much longer steel back plate and a steel pipe gusset from the bottom of the base plate to the middle of the arm, to provide reinforcing.
• A heavy duty 1000mm long square pipe (50mm x 50mm) that has a much longer steel back plate and a steel pipe gusset from the bottom of the base plate to the middle of the arm, to provide reinforcing.
• Both heavy duty arms can be used just like this (the extruded rubber top needs to be ordered separately, as it is not included in the price), or you can order them with 600mm heavy duty sliding rails and the outer part, which comes with comes with rubber on the top surface.

(1s and 2s), it is usual to support boats with just 2 arms. For this, the ideal span is 2.8m.

there is a choice of either 2 or 3 arms to support each boat. For 2 arms, you may choose a span of either 4.2m, or 5.6m. For 3 arms, you will need to have a double span of 2.8m.

it is usual to support boats with 3 arms. For this, the usual span is 5.6m, which is doubled to 11.2m.

3 cross stays will be needed, unless you have chosen to use 3 arms to support each boat, in which case you will need 6 cross stays.

4 cross stays will be needed, unless you have chosen to use 3 arms to support each boat, in which case you will need 8 cross stays.

2 uprights will be needed, unless you have chosen to use 3 arms to support each boat, in which case you will need 3 uprights.

4 uprights will be needed, unless you have chosen to use 3 arms to support each boat, in which case you will need 6 uprights.