CKR04-4-100-300 LESTA 100x300mm R300 ladder cross IEK CKR04-4-150-400 LESTA 150x400mm R300 staircase cross IEK CKR04-4-055-300 LESTA 55x300mm R300 ladder cross IEK CKR04-4-150-300 LESTA 150x300mm R300 staircase cross IEK CKR04-4-080-300 LESTA 80x300mm R300 ladder cross IEK CKR04-4-055-600 LESTA 55x600mm R300 staircase cross IEK CKR04-4-150-600 LESTA 150x600mm R300 staircase cross IEK CKR04-4-100-600 LESTA 100x600mm R300 staircase cross IEK